Consolidated Statement of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In-Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Noncontrolling Interests	Series C Preferred Stock Preferred Stock	Series I Preferred Stock Preferred Stock
Balance at Dec. 31, 2012	$ 6,907,103	$ 950	$ 4,667,900	$ (322,858)	$ (29,587)	$ 1,701,092	$ 487,301	$ 180,340	$ 221,965
Balance (in shares) at Dec. 31, 2012		91,250,000
Increase (Decrease) in Stockholders' Equity
Net income	59,656					53,751	5,905
Other comprehensive income	10,965				10,965
Preferred dividends	(14,406)					(14,406)
DRIP proceeds	26		26
Conversion of units of the Operating Partnership to common stock	17,287	2	17,285
Conversion of units of the Operating Partnership to common stock (in shares)		224,000
Reallocation of noncontrolling interest in the Operating Partnership	(36,091)					(36,091)
Amortization of deferred compensation plan	13,324		13,324
Amortization of deferred compensation plan (in shares)		4,000
Redemption of preferred stock	(192,500)					(12,160)		(180,340)
Preferred stock issuance costs	(33)								(33)
Issuance of common stock	8,511	1	8,510
Issuance of common stock (in shares)		95,000
Sale of treasury stock	6,090			6,090
Sale of treasury stock (in shares)		83,000
Proceeds from stock options exercised	8,969	2	8,967
Proceeds from stock options exercised (in shares)		157,000
Contributions to consolidated joint venture	3,364						3,364
Cash distributions to noncontrolling interests	(8,152)						(8,152)
Cash distribution declared ($0.66 per common share, none of which represented a return of capital for federal income tax purposes)	(60,899)					(60,899)
Balance at Jun. 30, 2013	$ 6,723,214	$ 955	$ 4,716,012	$ (316,768)	$ (18,622)	$ 1,631,287	$ 488,418		$ 221,932
Balance (in shares) at Jun. 30, 2013		91,812,771