Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive deficit Additional Paid in Capital, Common Stock Paid-in capital Amortization of Financing Costs Amortization of deferred financing costs Condensed Consolidated Balance Sheets Balance Sheet Available-for-sale Securities, Gross Realized Losses Loss on sale of investments available for sale Loss on sale of investments available for sale Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds Net proceeds from sale of investments available for sale Net proceeds from sale of investments available for sale Amortization of Debt Discount (Premium) Non-cash interest expense related to amortization of discount on exchangeable senior notes Non-cash interest expense related to amortization of discount on exchangeable senior notes Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Cash and cash equivalents, beginning of the period Cash and cash equivalents, end of the period Interest Paid, Net Interest paid, net of amounts capitalized Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable and accrued expenses Increase (Decrease) in Operating Capital [Abstract] Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Due from Related Parties, Current Receivables from related parties and affiliated real estate joint ventures Commitments and Contingencies Disclosure [Text Block] COMMITMENTS AND CONTINGENCIES Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Outstanding Common stock, shares outstanding Common Stock, Value, Issued Common stock, $0.01 par value, 300,000,000 shares authorized, 94,243,303 and 87,587,322 shares issued and outstanding at June 30, 2011 and December 31, 2010, respectively Cost of Revenue Property operations Debt Instrument, Unamortized Discount Discount on exchangeable senior notes Derivative Instruments and Hedging Activities Disclosure [Text Block] DERIVATIVES Development in Process Real estate under development Earnings Per Share, Diluted Diluted (in dollars per share) Equity Method Investments Disclosure [Text Block] Equity Method Investments Disclosure [Text Block] INVESTMENTS IN REAL ESTATE VENTURES Severance Costs Severance costs Income (Loss) from Equity Method Investments Equity in earnings of real estate ventures Share-based Compensation Compensation expense related to stock-based awards Payments of Financing Costs Deferred financing costs Gains (Losses) on Extinguishment of Debt Gain on repurchase of exchangeable senior notes Gain on repurchase of exchangeable senior notes General and Administrative Expense General and administrative Condensed Consolidated Statements of Operations Statement of Operations Net Income (Loss) Attributable to Noncontrolling Interest, Preferred Unit Holders Net income allocated to Preferred Operating Partnership noncontrolling interests Income Tax Disclosure [Text Block] Income Tax Disclosure [Text Block] INCOME TAXES Increase (Decrease) in Other Operating Assets Other assets Increase (Decrease) in Restricted Cash Change in restricted cash Interest Expense Interest expense Real Estate Investments, Unconsolidated Real Estate and Other Joint Ventures Investments in real estate ventures Liabilities and Stockholders' Equity [Abstract] Liabilities, Noncontrolling Interests and Equity: Liabilities and Stockholders' Equity Total liabilities, noncontrolling interests and equity Liabilities Total liabilities Long-term Line of Credit Lines of credit Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Distributions to Operating Partnership units held by noncontrolling interests Noncontrolling Interest Disclosure [Text Block] OTHER NONCONTROLLING INTERESTS Net Cash Provided by (Used in) Financing Activities [Abstract] Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Income (Loss) Available to Common Stockholders, Basic Net Income (Loss) Attributable to Parent Net income attributable to common stockholders Net income attributable to common stockholders Cash and Cash Equivalents, Period Increase (Decrease) Net decrease in cash and cash equivalents Noncontrolling Interest in Operating Partnerships Noncontrolling interests in Operating Partnership Operating Income (Loss) Income from operations Income (loss) from operations Revenues [Abstract] Revenues [Abstract] Revenues: Other Assets. Other assets, net Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax Change in fair value of interest rate swap Other Noncontrolling Interests; Other noncontrolling interests Other Notes Payable Notes payable to trusts Other Real Estate Revenue Other income Payments of Dividends, Common Stock Dividends paid on common stock Payments of Dividends, Noncontrolling Interest Distributions to noncontrolling interests (Operating Partnership and other) Preferred Stock, Shares Authorized Preferred stock, shares authorized Preferred Stock, Shares Issued Preferred stock, shares issued Noncontrolling Interest in Preferred Unit Holders Noncontrolling interest represented by Preferred Operating Partnership units, net of $100,000 note receivable Proceeds from Issuance of Common Stock Proceeds from the sale of common stock Net proceeds from issuance of common stock Proceeds from Noncontrolling Interests Investments from noncontrolling interests Proceeds from Sale of Other Real Estate Proceeds from sale of properties to joint venture Proceeds from Stock Options Exercised Net proceeds from exercise of stock options Payments to Acquire Commercial Real Estate Acquisition of real estate assets Payments for Construction in Process Development and construction of real estate assets Payments to Acquire Equity Method Investments Investments in real estate ventures Real Estate Disclosure [Text Block] Real Estate Disclosure [Text Block] REAL ESTATE ASSETS Real Estate Investment Property, Net Net real estate assets Real Estate Revenue, Net Total revenues Total revenues Due from Related Parties, Noncurrent Note receivable from noncontrolling interest represented by Preferred Operating Partnership units (in dollars) Note receivable from Preferred Operating Partnership unit holder Loan to holders of preferred OP units Related Party Transactions Disclosure [Text Block] Related Party Transactions Disclosure [Text Block] RELATED PARTY AND AFFILIATED REAL ESTATE JOINT VENTURE TRANSACTIONS Repayments of Unsecured Debt Repurchase of exchangeable senior notes Payments to Noncontrolling Interests Redemption of Operating Partnership units held by noncontrolling interest Retained Earnings (Accumulated Deficit) Accumulated deficit Management Fees Revenue Management and franchise fees Schedule of Line of Credit Facilities [Table Text Block] Schedule of Line of Credit Facilities [Text Block] LINES OF CREDIT Secured Debt Notes payable Segment Reporting Disclosure [Text Block] SEGMENT INFORMATION Condensed Consolidated Statements of Cash Flows Statement of Cash Flows Condensed Consolidated Statement of Equity Condensed Consolidated Statement of Equity Stockholders' Equity Attributable to Parent [Abstract] Extra Space Storage Inc. stockholders' equity: Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] Supplemental schedule of cash flow information Weighted Average Number of Shares Outstanding, Diluted Diluted (in shares) Average number of common shares outstanding - diluted (in shares) Weighted Average Number of Shares Outstanding, Basic Basic (in shares) Average number of common shares outstanding - basic (in shares) Common Stock Reinsurance Premiums for Insurance Companies, by Product Segment, Gross Amount Tenant reinsurance Assets Total assets Total assets Investment Income, Interest Interest income Due from Related Parties Receivables from related parties and affiliated real estate joint ventures Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] STOCK-BASED COMPENSATION Scenario, Unspecified [Domain] Statement [Table] Statement, Scenario [Axis] Income (Loss) from Equity Method Investments, Net of Dividends or Distributions Distributions from real estate ventures in excess of earnings Assets [Abstract] Assets: Statement Statement [Line Items] Payments to Acquire Furniture and Fixtures Purchase of equipment and fixtures Other Liabilities. Other liabilities Earnings Per Share, Basic Basic (in dollars per share) Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Stockholders' Equity, Period Increase (Decrease) Stockholders' Equity, Period Increase (Decrease) Preferred Stock, Par or Stated Value Per Share Preferred stock, par value (in dollars per share) Common Stock, Shares, Issued Common stock, shares issued Balances (in shares) Balances (in shares) Preferred Stock, Shares Outstanding Preferred stock, shares outstanding Real Estate Investment Property, Net [Abstract] Real estate assets: Earnings Per Share [Abstract] Net income per common share Increase (Decrease) in Other Operating Liabilities Other liabilities Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest Income before equity in earnings of real estate ventures and income tax expense Common Stock, Par or Stated Value Per Share Common stock, par value (in dollars per share) Stockholders' Equity Attributable to Parent Total Extra Space Storage Inc. stockholders' equity Income Tax Expense (Benefit) Income tax expense Preferred Stock, Value, Issued Preferred stock, $0.01 par value, 50,000,000 shares authorized, no shares issued or outstanding Common Stock, Dividends, Per Share, Cash Paid Cash dividends paid per common share (in dollars per share) Dividends paid on common stock, per share (in dollars per share) Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Redemption of Operating Partnership units for cash Redemption of Operating Partnership units for common stock Statement, Equity Components [Axis] Paid-in Capital Accumulated Deficit Accumulated Other Comprehensive Deficit Equity Component [Domain] Equity Component [Domain] Long-term Debt [Text Block] Long-term Debt [Text Block] NOTES PAYABLE Stock Issued During Period, Value, Restricted Stock Award, Gross Restricted stock grants issued Stock Issued During Period, Value, Restricted Stock Award, Forfeitures Stock Issued During Period, Value, Restricted Stock Award, Forfeitures Restricted stock grants cancelled Stock Issued During Period, Value, Stock Options Exercised Issuance of common stock upon the exercise of options Stock Issued During Period, Shares, Restricted Stock Award, Gross Restricted stock grants issued (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Forfeited Restricted stock grants cancelled (in shares) Stock Issued During Period, Shares, Stock Options Exercised Issuance of common stock upon the exercise of options (in shares) Stock Issued During Period, Shares, Period Increase (Decrease) Stock Issued During Period, Shares, Period Increase (Decrease) Other Liabilities Disclosure [Text Block] Other Liabilities Disclosure [Text Block] OTHER LIABILITIES Stock Issued During Period, Value, Conversion of Units Conversion of Operating Partnership units to common stock Stock Issued During Period, Shares, Conversion of Units Conversion of Operating Partnership units to common stock (in shares) Comprehensive Income Costs and Expenses [Abstract] Costs and Expenses [Abstract] Expenses: Costs and Expenses Total expenses Operating expenses, including depreciation and amortization Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Supplemental schedule of noncash investing and financing activities: Dividends, Common Stock Dividends paid on common stock at $0.28 per share Adjustments to Additional Paid in Capital, Tax Effect from Share-based Compensation Tax effect from vesting of restricted stock grants and stock option exercises Earnings Per Share [Text Block] NET INCOME PER COMMON SHARE Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Net income Net income (loss) Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Weighted Average Number of Shares Outstanding, Diluted, Disclosure Items [Abstract] Weighted average number of shares Weighted average common shares outstanding: Depreciation, Depletion and Amortization Depreciation and amortization Total depreciation and amortization expense Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Comprehensive Income, Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Comprehensive income: Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Total comprehensive income Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Equity : Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total noncontrolling interests and equity Balances Balances Accounts Payable and Accrued Liabilities Accounts payable and accrued expenses Noncontrolling Interest [Member] Noncontrolling Interests Extra Space Storage Inc. Stockholders' Equity Restricted Cash and Cash Equivalents Restricted cash Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Nature of Operations [Text Block] ORGANIZATION Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition, Value Compensation expense related to stock-based awards Stockholders' Equity, Other Deconsolidation of noncontrolling interests Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt Repurchase of equity portion of exchangeable senior notes BASIS OF PRESENTATION Basis of Presentation [Text Block] This element encapsulates disclosures pertaining to reclassifications, recently issued accounting pronouncements, fair value disclosures and others for the entity. NOTES PAYABLE TO TRUSTS Notes Payable to Trusts Disclosure [Text Block] This element encapsulates details pertaining to notes payable to trusts. EXCHANGEABLE SENIOR NOTES Exchangeable Senior Notes Disclosure [Text Block] This element encapsulates disclosures pertaining to exchangeable senior notes of the entity. NONCONTROLLING INTEREST REPRESENTED BY PREFERRED OPERATING PARTNERSHIP UNITS Noncontrolling Interest Represented by Preferred Operating Partnership Units Disclosure [Text Block] This element encapsulates disclosures pertaining to noncontrolling preferred operating partnership of the entity. NONCONTROLLING INTEREST IN OPERATING PARTNERSHIP Noncontrolling Interest in Operating Partnership Disclosure [Text Block] This element encapsulates disclosures pertaining to noncontrolling ordinary operating partnership of the entity. Having secondary preference to preferred operating partnerships. UNRECOVERED DEVELOPMENT AND ACQUISITION COSTS AND SEVERANCE COSTS ASSOCIATED WITH THE WIND-DOWN OF DEVELOPMENT PROGRAM Unrecovered Development, Acquisition and Severance Costs Disclosure [Text Block] This element encapsulates disclosures pertaining to unrecovered development and acquisition costs including due diligence costs that was part of an unsuccessful attempt by the entity. Tenant reinsurance Tenant Reinsurance, Expense The costs that are incurred to provide tenant reinsurance. Interest income on note receivable from Preferred Operating Partnership unit holder Interest Income on Note Receivable from Preferred Partnership Unit Holders Value of interest income on loan to the holders of preferred operating partnership units. Net income allocated to Operating Partnership and other noncontrolling interests Minority Interest in Net Income (Loss) Operating Partnerships and Other Amount of net income (loss) for the period allocated to noncontrolling partners of an operating partnership and others included in the entity's consolidated financial statements. Preferred Operating Partnership Noncontrolling interest represented by the operating partnership having preferential rights over other operating partnerships. Operating Partnership Noncontrolling interest represented by the ordinary operating partnership. Other noncontrolling interests. Other noncontrolling interests in properties. Other Noncontrolling Interests Investments from other noncontrolling interests Adjustments in Investments from Other Noncontrolling Interests Element represents adjustments to investments from other noncontrolling interests. Document and Entity Information Unrecovered Development and Acquisition Costs Unrecovered development and acquisition costs The costs incurred for unsuccessful development and acquisition activities. It includes asset impairment expenses for such unsuccessful development and acquisition activities. Proceeds from Notes Payable and Lines of Credit Proceeds from notes payable and lines of credit The cash inflow from a borrowing supported by a written promise and contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity that is collateralized (backed by pledge, mortgage or other lien in the entity's assets). Principal payments on notes payable and lines of credit Payments of Notes Payable and Lines of Credit The cash outflow for a borrowing supported by a written promise and contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity. Net operating real estate assets Net Operating Real Estate Assets The carrying amount of real estate assets including land, buildings, improvements, intangible assets and intangible lease rights, net of accumulated depreciation and amortization. Return of investment in real estate ventures Return of Investment, Real Estate Ventures Distributions that represent a return of original investment from real estate ventures. BASIS OF PRESENTATION NOTES PAYABLE TO TRUSTS EXCHANGEABLE SENIOR NOTES NONCONTROLLING INTEREST REPRESENTED BY PREFERRED OPERATING PARTNERSHIP UNITS NONCONTROLLING INTEREST IN OPERATING PARTNERSHIP UNRECOVERED DEVELOPMENT AND ACQUISITION COSTS AND SEVERANCE COSTS ASSOCIATED WITH THE WIND-DOWN OF DEVELOPMENT PROGRAM Adjustments to Additional Paid in Capital, Tax Effect from Wind Down of Development Program Tax effect from wind down of development program Tax benefit associated with the wind down of the development program. The tax benefit results from the deduction by the entity on its tax return for impairments relating to changes in fair value. Includes any resulting tax benefit that exceeds the previously recognized deferred tax asset (excess tax benefits). Deconsolidation of joint ventures due to application of Accounting Standards Codification 810: This item represents the Deconsolidation of joint ventures due to application of Accounting Standards Codification 810. Deconsolidation of Joint Ventures Due to Application of Accounting Standards Codification 810 Real Estate Assets. Real estate assets noncash investing and financing activities due to application of Accounting Standards Codification 810. Real estate assets, net Investment In Real Estate Ventures Investment in Real Estate Ventures noncash investing and financing activities due to application of Accounting Standards Codification 810. Investments in real estate ventures Other Assets and Other Liabilities Other Assets and Other Liabilities noncash investing and financing activities due to application of Accounting Standards Codification 810. Other assets and other liabilities Notes Payable Non Cash Notes Payable noncash investing and financing activities due to application of Accounting Standards Codification 810. Notes payable Other Noncontrolling Interests, Other Noncontrolling interests noncash investing and financing activities due to application of Accounting Standards Codification 810. Other noncontrolling interests Investments from other noncontrolling interests Proceeds From Sale Of Interest In Partnership Unit Minority Interest Increase from Purchase of Interests Purchase of noncontrolling interest This element represents the increase in noncontrolling interest due to the purchase of noncontrolling interests whose accounts were in a negative position due to allocation of losses. Proceeds from Sale of Real Estate Held-for-investment Proceeds from sale of real estate assets Stock Issued During Period, Value, Conversion of Convertible Securities Conversion of Contingent Conversion shares to common stock Stock Issued During Period, Value, New Issues Issuance of common stock, net of offering costs Stock Issued During Period, Shares, New Issues Issuance of common stock, net of offering costs (in shares) Issuance of common stock (in shares) Related Party Receivables Related party receivables noncash investing and financing activities due to application of Accounting Standards Codification 810. Receivables from related parties and affiliated real estate joint ventures Acquisitions of real estate assets Noncash or Part Noncash Acquisition, Net Real Estate Assets Acquired [Abstract] Noncash or Part Noncash Acquisition Net Real Estate Assets Acquired Real estate assets, net Represents the amount of real estate assets that an Entity acquires in a noncash (or part noncash) acquisition. Real estate assets refer to the lands, buildings and intangible assets (including those that are part of operations and those under development) of a real estate entity, net of accumulated depreciation and amortization. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period. Unrecovered Development And Acquisition Costs Noncash Unrecovered development and acquisition costs The costs incurred for unsuccessful development and acquisition activities. It includes Non-cash asset impairment expenses for such unsuccessful development and acquisition activities. Loss on sublease Loss on Sublease Loss incurred as a result of subletting office space under a long-term office lease assumed in an acquisition. Stock Issued During Period, Shares, Conversion of Convertible Securities Conversion of Contingent Conversion shares to common stock (in shares) Available-for-sale Securities [Table Text Block] Available-for-sale Securities [Text Block] INVESTMENTS AVAILABLE FOR SALE Quarterly Financial Information [Text Block] Quarterly Financial Information [Text Block] SUPPLEMENTARY QUARTERLY FINANCIAL DATA (UNAUDITED) Significant Accounting Policies [Text Block] Significant Accounting Policies [Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Pension and Other Postretirement Benefits Disclosure [Text Block] Pension and Other Postretirement Benefits Disclosure [Text Block] EMPLOYEE BENEFIT PLAN STOCK OFFERING Stockholders' Equity Note Disclosure [Text Block] Noncontrolling interest consolidated as business acquisition Noncontrolling interest consolidated as business acquisition This element represents the increase in noncontrolling interest due to the consolidation of business acquisitions. Adjustments to Additional Paid In Capital Tax Effect from Contribution of Property to Subsidiary Tax effect from contribution of property to Taxable REIT Subsidiary This line item represents the tax effect adjustment to additional paid-in-capital from the contribution of property to subsidiary. New Operating Partnership units issued Monetary value of the issuance of new units of limited partnership interest as part of a property acquisition. Partner Capital Account Units Issued Operating Partnership Units Issued Operating Partnership units issued as consideration The value of the issuance of new units of limited partnership interest in noncash financing activities. Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax Loss on sale of investments available for sale VARIABLE INTERESTS Noncontrolling Interest [Table] Noncontrolling Interest [Table] Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Other Noncontrolling Interests Noncontrolling interest represented by preferred operating partnership units Noncontrolling interest in operating partnership Number of Real Estate Properties under Lease-up Stage Number of consolidated self-storage properties under lease-up stage The number of real estate properties owned under lease-up stage as of the balance sheet date. Minority Interest Ownership Percentage by Noncontrolling Owners, High End of Range Ownership interests of third party owners, high end of range (as a percent) The high end of range of equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity. Minority Interest Ownership Percentage by Noncontrolling Owners, Low End of Range Ownership interests of third party owners, low end of range (as a percent) The low end of range of equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity. Noncontrolling Interest Repurchase of Real Estate Properties, Number Number of self-storage properties in which minority partners' membership interests is acquired The number of real estate properties attributable to noncontrolling interests repurchased during the year. Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of financial information of business segments Property management, acquisition and development Represents Property management, acquisition and development segment of the entity. Rental operations Represents Rental operations segment of the entity. Tenant reinsurance Represents Tenant reinsurance segment of the entity. Reporting Segments Number Number of reportable segments The number of reportable segments of the entity. Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Statement, Business Segments [Axis] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Segment Information Interest and Debt Expense Interest expense Depreciation, Depletion and Amortization [Abstract] Depreciation, Depletion and Amortization [Abstract] Depreciation and amortization expense Number of Real Estate Properties Franchisees and Others Number of properties owned by franchisees and third parties The number of real estate properties owned by franchisees and other third parties as of the balance sheet date. Number of Real Estate Properties Owned and or Managed Number of operating properties owned and/or managed The number of real estate properties owned and/or managed as of the balance sheet date. Number of Real Estates Construction in Process The number of real estate properties construction in process as of the balance sheet date. Number of consolidated self-storage properties under development Maximum Percentage of Rental Income Accounted for by Single Tenant Maximum percentage of rental income accounted for by any single tenant (as a percent) Represents the maximum percentage of rental income accounted for by any single tenant. Fair Value, by Balance Sheet Grouping [Text Block] Schedule of fair value of financial instruments Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value of Financial Instruments Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Estimate of Fair Value, Fair Value Disclosure [Member] Carrying (Reported) Amount, Fair Value Disclosure [Member] Fair Value, Disclosure Item Amounts [Domain] Fair Value, Disclosure Item Amounts [Domain] Income (Loss) Attributable to Noncontrolling Interest Fixed Component Subtract: Fixed component of income allocated to noncontrolling interest - Preferred Operating Partnership Represents the component of income or loss attributable to the noncontrolling interest as a result of fixed distributions paid to Preferred Operating unit holders. Incremental Common Shares Attributable to Conversion of Operating Partnership Units Operating Partnership units (in shares) Shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible operating partnership units. Incremental Common Shares Attributable to Conversion of Preferred Operating Partnership Units Preferred Operating Partnership units (in shares) Shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible preferred operating partnership units. Fair Value, Inputs, Level 1 [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Significant Unobservable Inputs (Level 3) Interest Rate Cash Flow Hedge Derivative at Fair Value, Net Cash Flow Hedge Swap Agreements Fair value of cash flow hedge swap agreements Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping, Disclosure Item Amounts [Axis] Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Computation of net income per common share Schedule of Earnings Per Share [Table] Tabular disclosure pertaining to the entity's earnings per share. Earning Per Share [Line Items] Net income per common share Debt Instrument, Percentage of Exchange Price Used to Determine Price Per Share that Must be Exceeded for Conversion Percentage of exchange price used to determine the minimum stock price that must be exceeded for exchangeable notes to be exchanged (as a percent) This element represents the percentage of exchange price used to calculate the minimum stock price that must be exceeded for exchangeable notes to be exchanged by debt holders. Preferred Operating Partnership Units Convertible Carrying Amount of the Equity Component Settled in Cash Minimum Exchangeable preferred operating partnership units settled in cash, minimum Represents the minimum amount of equity component of convertible preferred operating partnership units which will be settled in cash upon conversion. Net Income (Loss) Available to Common Stockholders, Diluted Net income for diluted computations Incremental Common Shares Attributable to Share-based Payment Arrangements Dilutive and cancelled stock options (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Anti-dilutive share options excluded from computation of earnings per share (in shares) Schedule of Guarantor Obligations [Table Text Block] Schedule of guaranteed loans for unconsolidated joint ventures Extra Space of Montrose Avenue LLC Represents Extra Space of Montrose Avenue LLC, a joint venture of the entity. Extra Space of Sacramento One LLC Represents Extra Space of Sacramento One LLC, a joint venture of the entity. ESS Baltimore LLC Represents ESS Baltimore LLC. Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Variable Interest Entities by Classification of Entity [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Investments in and Advances to Affiliates Categorization [Axis] Investments in and Advances to Affiliates Categorization [Domain] Investments in and Advances to Affiliates Categorization [Domain] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Commitments And Contingencies Guarantor Obligations, Maximum Exposure, Undiscounted Guaranteed loan amount Balance of guaranteed loan Schedule of Real Estate Property Acquisitions [Table] Schedule of operating properties acquired by location and acquisition date including consideration paid and acquisition date fair value. Acquisition Date Fair Value, Land The amount of acquisition cost of a real estate property allocated to land. Real Estate Property Acquisition Purchase Price Allocation Land Real Estate Property Acquisition Purchase Price Allocation Building Acquisition Date Fair Value, Building The amount of acquisition cost of a real estate property allocated to building. Real Estate Property Acquisition Closing Costs Expensed Closing costs - expensed Represents closing costs expensed related to real estate property acquired. Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Schedule of balance sheet classification and carrying amounts of the interest rate swaps Real Estate Property Acquisitions [Axis] Represents information regarding acquisitions of operating properties aggregated according to factors such as location, number of properties and acquisition date. Real Estate Properties Acquisition [Line Items] Property Acquisitions Number of Real Estate Properties Acquired Number of Properties Represents the number of real estate properties acquired. Number of self-storage facilities (properties) acquired Real Estate Property Acquisition Assets Acquired Liabilities Assumed, Net Net Liabilities (Assets) Assumed The net value of assets transferred or liabilities assumed in connection with the acquisition of real estate operating property. Notional Amount of Interest Rate Cash Flow Hedge Derivatives, Low End of Range Notional amount of cash flow hedge swap agreements, low end of range The low end of the range of the aggregate notional amount of all interest rate derivatives designated as hedging instruments in cash flow hedges. Notional amount refers to the monetary amount specified in the interest rate derivative contract. Notional Amount of Interest Rate Cash Flow Hedge Derivatives, High End of Range Notional amount of cash flow hedge swap agreements, high end of range The high end of the range of the aggregate notional amount of all interest rate derivatives designated as hedging instruments in cash flow hedges. Notional amount refers to the monetary amount specified in the interest rate derivative contract. Derivative, Lower Fixed Interest Rate Range Strike rate cash flow hedge swap agreements, low end of range (as a percent) Derivative, Higher Fixed Interest Rate Range Strike rate cash flow hedge swap agreements, high end of range (as a percent) Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net Cash flow hedge swap agreements gain (loss) reclassified from OCI Number of Condominiums Held-for-sale Number of vacant condominiums held for sale Represents the number of vacant condominiums that the entity intends to sell. Fair Value Assets and Liabilities Measured on Nonrecurring Basis [Abstract] Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis Interest Rate Cash Flow Hedge Increase (Decrease) in Interest Expenses Due to Interest Payments Cash flow hedge swap agreements increase (decrease) in interest expenses due to interest payments Represents the increase or decrease recognized in interest expenses due to interest payments under cash flow hedge swap agreements. Schedule of Derivative Instruments Interest Payments Impact on Interest Expenses [Table Text Block] Tabular disclosure of impact of interest payments on interest expenses recognized under cash flow hedge swap agreements. Schedule of monthly interest payments recognized as an increase or decrease in interest expense Guarantee Obligations, Estimated Fair Value of Assets The estimated fair value of any assets held either as collateral or by third parties that, upon the occurrence of any triggering event or condition under the guarantee, the guarantor can obtain and liquidate to recover all or a portion of the amounts paid under the guarantee. Estimated fair market value of assets Net Income (Loss) Attributable to Noncontrolling Interest Add: Income allocated to noncontrolling interest - Preferred Operating Partnership and Operating Partnership Schedule of Derivative Instruments [Table Text Block] Schedule summarizing the terms of derivative financial instruments Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance [Table Text Block] Schedule of information relating to the gains recognized on the swap agreements Variable Interest Entity Not Primary Beneficiary Joint Ventures Comparison of Carrying Amount of Liabilities to Maximum (Loss) Exposure [Table Text Block] Schedule of the comparison of the liability balance and the maximum exposure to loss related to the VIE JVs A tabular comparison of the carrying amounts of liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the unconsolidated VIE joint ventures and the reporting entity's maximum exposure to loss as a result of its involvement with the VIE. Variable Interest Entity Not Primary Beneficiary Comparison of Carrying Amount of Liabilities to Maximum (Loss) Exposure [Table Text Block] Schedule of the comparison of the liability balance and the maximum exposure to loss related to trusts A tabular comparison of the carrying amounts of liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the subsidiaries of operating partnership and the reporting entity's maximum exposure to loss as a result of its involvement with the VIE. Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] Corporate Joint Venture [Member] Trust Represents ESS Statutory Trust I, a wholly-owned, unconsolidated subsidiary of the operating partnership of the entity. Trust II Represents ESS Statutory Trust II, a wholly-owned, unconsolidated subsidiary of the operating partnership of the entity. Trust III Represents ESS Statutory Trust III, a wholly-owned, unconsolidated subsidiary of the operating partnership of the entity. Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Variable Interests in Unconsolidated Real Estate Joint Ventures: Variable Interest Entity, Interest in Joint Ventures Number Number of interests in unconsolidated VIE joint ventures Represents the number of unconsolidated VIE joint ventures in which the entity holds interest. Equity Method Investment, Ownership Percentage Low End of Range Equity interests in unconsolidated VIE joint ventures, low end of range (as a percent) The low end of the range of the percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. Equity Method Investment, Ownership Percentage High End of Range Equity interests in unconsolidated VIE joint ventures, high end of range (as a percent) The high end of the range of the percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. Represents the stated interest rate of notes receivable. Notes Receivable Stated Interest Rate Note receivable interest rate (as a percent) Noncontrolling Interest Conversion of Preferred Operating Partnership Units before Maturity of Loan, Maximum Maximum number of preferred OP units converted prior to the maturity date of the loan (in units) Represents the maximum number of preferred operating partnership units that can be converted by noncontrolling holders of preferred units before maturity date of the loan. Noncontrolling Interest in Preferred Operating Partnership Units, Fixed Priority Return, Amount Fixed priority return on preferred OP units, amount Represents the carrying amount of preferred operating partnership units attributable to noncontrolling preferred unit holders on which the fixed priority return is granted. Equity Method Investments Investment balance Due from Joint Ventures Payables to company Variable Interest Entity, Interest in Trust, Number Number of wholly-owned unconsolidated subsidiaries Represents the number of wholly-owned unconsolidated subsidiaries. Variable Interest Entity in Trust Carrying Amount of Liabilities to Maximum Loss Exposure [Abstract] Comparison of the liability balance and the maximum exposure to loss related to trusts Variable Interest Entity, Ownership Percentage Voting rights in unconsolidated VIE joint ventures (as a percent) Investment balance Represents the carrying amount on the entity's balance sheet of its investment in unconsolidated subsidiaries. Variable Interest Entity in Trust, Investment Amount Noncontrolling Interest in Preferred Operating Partnership Units, Fixed Priority Return, Stated Rate of Return Fixed priority return on preferred OP units, stated return rate (as a percent) Represents the carrying amount of preferred operating partnership units attributable to noncontrolling preferred unit holders on which the fixed priority return is granted. Noncontrolling Interest in Preferred Operating Partnership Units, Fixed Priority Return, Redemption Value Fixed priority return on preferred OP units, liquidation value Represents the liquidation value of preferred operating partnership units attributable to noncontrolling preferred unit holders on which the fixed priority return is granted. Noncontrolling Interest, Ownership Percentage by Parent Ownership interest held by entity (as a percent) Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Noncontrolling interest in operating partnership (as a percent) Units of Partnership Interest, Amount Common OP units outstanding (in units) Average Closing Market Price Measurement Period Number of days used as a denomination to determine the average closing price of common stock (in days) Represents the average market closing price measurement period. Common Stock, Average Closing Market Price Ten day average closing stock price (in dollars per share) This element represents the average closing market price of the common stock. Variable Interest, Difference (Between Carrying Amount and Maximum Exposure) Difference Real Estate Property Acquisition [Domain] Represents operating property acquisitions. New York, 1 Property Acquired 5/21/2010 Represents the property acquired in the state of New York on 5/21/2010. Georgia, 3 Properties Acquired 6/17/2010 Represents the three properties acquired in the state of Georgia on 6/17/2010. Notes Payable, Fair Value Disclosure Fixed rate notes payable and notes payable to trusts COMMITMENTS AND CONTINGENCIES Debt Instrument, Convertible, Conversion Price Exchangeable senior notes exchange price per share (in dollars per share) Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Assets and Liabilities Measured at Fair Value on a Recurring Basis Recurring basis Noncash or Part Noncash Acquisition, Debt Assumed Notes payable Loan Assumed Notes payable Number of Real Estate Properties Number of operating storage facilities in which the entity has equity interests Number of properties purchased Number of States in which Entity Operates Number of states in which operating storage facilities are located Other Assets Disclosure [Text Block] OTHER ASSETS OTHER LIABILITIES Property Management Fee, Percent Fee Management fees charged from unconsolidated VIE joint ventures (as a percent) Schedule III Real Estate and Accumulated Depreciation Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of assets and liabilities measured at fair value on a recurring basis Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of computation of net income per common share Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss) Cash flow hedge swap agreements gain (loss) recognized in OCI Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Maximum exposure to loss Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities Liability balance The Trusts Noncash or Part Noncash Acquisition, Accounts Receivable Acquired Change in receivables from related parties and affiliated real estate joint ventures due to consolidation of joint venture properties Redemption of Operating Partnership units held by noncontrolling interests for common stock Conversion of Stock, Amount Converted Operating Leases, Income Statement, Minimum Lease Revenue Property rental Commitments and Contingencies. Commitments and contingencies Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Segment [Domain] Fair Value by Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] DERIVATIVES SEGMENT INFORMATION Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Amendment Description Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Convertible Debt Exchangeable senior notes PROPERTY ACQUISITIONS Business Combination Disclosure [Text Block] Variable Interests Disclosure [Text Block] VARIABLE INTERESTS Represents the disclosure of variable interests. Schedule of Business Acquisitions, by Acquisition [Table Text Block] Schedule of operating properties acquired Real Estate Remaining Development Projects in Process, Number Number of development projects in process The number of remaining development projects in process as of the balance sheet date. Convertible Debt, Fair Value Disclosures Exchangeable senior notes Business Acquisition, Cost of Acquired Entity, Purchase Price Total Consideration Paid Business Acquisition, Cost of Acquired Entity, Cash Paid Cash Consideration Paid Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets Acquisition Date Fair Value, Intangible Preferred Units Issued in Exchange as Part of Acquisition Preferred OP units (in units) The number of preferred units issued in exchange as part of an acquisition. Basis of Exchange Operating Partnership Units for Common Stock Common OP units conversion basis Represents the basis of exchange for the entity's option to acquire operating partnership units in exchange for shares of its common stock. Cash consideration on redemption of common OP units Operating Partnership Units, Redemption Amount Represents the amount the entity would have paid in cash to redeem the operating partnership units. Real Estate Consolidated Self Storage Properties, Number Number of consolidated self-storage properties Represents the number of consolidated self-storage properties as of the balance sheet date. Payments for Repurchase of Noncontrolling Interest Payment to acquire minority partners' interests in consolidated self-storage properties The cash outflow during the period for redemption of noncontrolling interests. FAIR VALUE DISCLOSURES Fair Value Disclosures [Text Block] FAIR VALUE DISCLOSURES STOCK OFFERING Utah, Texas, 2 Properties Acquired 4/1/2011 Represents the two properties acquired in the state of Utah, Texas on 4/1/2011. California, 1 Property Acquired 2011/04/07 Represents the property acquired in the state of California on 4/7/2011. Texas, 1 Property Acquired 2011/04/15 Represents the property acquired in the state of Texas on 4/15/2011. Colorado, 1 Property Acquired 2011/05/25 Represents the property acquired in the state of Colorado on 5/25/2011. Virginia, 1 Property Acquired 2011/05/26 Represents the property acquired in the state of Virginia on 5/26/2011. New Jersey, 1 Property Acquired 2011/06/02 Represents the property acquired in the state of New Jersey on 6/2/2011. Colorado, 1 Property Acquired 2011/06/10 Represents the property acquired in the state of Colorado on 6/10/2011. Payments to Acquire Interest in Joint Venture Cash paid to obtain joint venture partner's equity interests in joint venture Stock Issued During Period Price Per Share New Issues Price per share of common stock issued during period (in dollars per share) Represents the price per share at which common stock was issued during the period. Gross Proceeds from Issuance of Common Stock Gross proceeds from issuance of common stock Represents the cash inflow from the additional capital raised by the entity through public stock offering. Payments of Stock Issuance Costs Transaction costs of stock issuance ORGANIZATION PROPERTY ACQUISITIONS OTHER NONCONTROLLING INTERESTS SUBSEQUENT EVENTS SUBSEQUENT EVENTS Subsequent Events [Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES REAL ESTATE ASSETS INVESTMENTS IN REAL ESTATE VENTURES NOTES PAYABLE RELATED PARTY AND AFFILIATED REAL ESTATE JOINT VENTURE TRANSACTIONS STOCK-BASED COMPENSATION INCOME TAXES EMPLOYEE BENEFIT PLAN SUPPLEMENTARY QUARTERLY FINANCIAL DATA (UNAUDITED) Earnings Per Share, Basic and Diluted [Abstract] NET INCOME PER COMMON SHARE OTHER ASSETS Redemption of Operating Partnership units for common stock (in shares) Minority Interest (Decrease) from Redemptions Shares This element represent as Redemption of Operating Partnership units for common stock. Nevada, 1 Property Acquired 2011/06/22 Represents the property acquired in the state of Nevada on 06/22/2011. Tennessee, 1 Property Acquired 2011/04/15 Represents the property acquired in the state of Nevada on 06/22/2011. Ohio, Indiana , Kentucky, 15 Properties Acquired 2011/06/27 Represents the properties acquired in the state of Ohio, Indiana, kentucky on 06/27/2011. Minority Interest (Decrease) from Cash Redemptions Decrease in noncontrolling interest balance from payment of cash dividends by the non-wholly owned subsidiary or partially owned entity, included in the consolidation of the parent entity, to the noncontrolling interest holders Redemption of Operating Partnership units for cash Subsequent Event [Table] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Acquisition Maryland 1 Property Member Represents the one property acquired in the state of Maryland. Texas 1 property acquired Represents the one property acquired in the state of Texas. Subsequent event Subsequent Event [Line Items] Distributions to other noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest, Other