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	29,217					26,316	2,901
Other comprehensive income	3,470				3,470
Preferred dividends	(7,407)					(7,407)
DRIP proceeds	13		13
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	(24,016)					(24,016)
Amortization of deferred compensation plan	7,822		7,822
Amortization of deferred compensation plan (in shares)		2,000
Preferred stock issuance costs	(33)								(33)
Common stock issuance costs	(24)		(24)
Proceeds from stock options exercised	4,533	1	4,532
Proceeds from stock options exercised (in shares)		79,000
Contributions to consolidated joint venture	3,110						3,110
Cash distributions to noncontrolling interests	(4,879)						(4,879)
Cash distribution declared ($0.33 per common share, none of which represented a return of capital for federal income tax purposes)	(30,517)					(30,517)
Balance at Mar. 31, 2013	$ 6,905,679	$ 953	$ 4,697,528	$ (322,858)	$ (26,117)	$ 1,665,468	$ 488,433	$ 180,340	$ 221,932
Balance (in shares) at Mar. 31, 2013	91,555,082	91,555,000