Noncontrolling Interests on the Company's Consolidated Financial Statements (Details) (USD $)	9 Months Ended
Sep. 30, 2011 NumberofTradingDays Years RSF NumberofBuildings Share_Based_Incentive_Compensation_Plans	Dec. 31, 2010	Sep. 30, 2010
Noncontrolling Interest (Textuals) [Abstract]
Percentage of general partnership interest owned by the company in the Operating Partnership	97.10%	96.80%	96.80%
Percentage of Common limited partnership interest owned by certain non-affiliated investors and certain directors and officers of the Company in the Operating Partnership	2.90%	3.20%	3.20%
Common units outstanding held by common limited partners	1,718,131	1,723,131	1,723,131
Conversion ratio of common units for common stock	one-for-one basis
Common stock, par value	$ 0.01	$ 0.01
Number of trading days	10
Aggregate value upon redemption of outstanding noncontrolling common units	$ 56,200,000	$ 61,400,000
Series A Preferred Units [Member]
Temporary Equity [Line Items]
7.45% Series A cumulative redeemable preferred units of the Operating Partnership outstanding	1,500,000	1,500,000
Preferred units redemption value per unit	$ 50	$ 50
Changes to noncontrolling interest	$ 0

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Noncontrolling Interest Textuals Abstract.

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Number of trading days immediately preceding the applicable balance sheet date used to calculate the redemption value of the outstanding noncontrolling common units of the Company.

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Face amount or stated value of common stock per share; generally not indicative of the fair market value per share.

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The number of limited partner units outstanding.

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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The fair value as of the reporting date of noncontrolling interests which are redeemable by the (parent) entity (1) at a fixed or determinable price on a fixed or determinable date, (2) at the option of the holder of the noncontrolling interest, or (3) upon occurrence of an event that is not solely within the control of the (parent) entity. The noncontrolling interest holder's ownership (or holders' ownership) may be in the form of common shares (regardless of class), limited partnership units (regardless of class), non-preferential membership interests, or any other form of common equity regardless of investee entity legal form.

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Change in the value of each type or class of stock classified as temporary equity during the period. The redemption requirement does not constitute an unconditional obligation that will be settled in a variable number of shares constituting a monetary value predominantly indexed to (a) a fixed monetary amount known at inception, (b) an amount inversely correlated with the residual value of the entity, or (c) an amount determined by reference to something other than the fair value of issuer's stock. Does not include mandatorily redeemable stock. The exception is if redemption is required upon liquidation or termination of the reporting entity.

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Amount to be paid per share that is classified as temporary equity by entity upon redemption. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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