Consolidated Statements of Equity (USD $) In Thousands, unless otherwise specified	Total	Redeemable Noncontrolling Partnership Interests [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Total Shareholders' Equity [Member]	Noncontrolling Interest [Member]	Parent [Member]
Balance, redeemable noncontrolling partnership interests at Dec. 31, 2010		$ 34,379
Balance at Dec. 31, 2010			23	1,479	1,657,507	7,855	(366,526)	1,300,338	223,605	1,523,943
Net income							47,319	47,319	10,151	57,470
Other Comprehensive Income	1,917	16				1,493		1,493	408	1,901
Conversion of operating partnership special common units to shares of common stock				1	728			729	(729)
Dividends declared - common stock							(31,150)	(31,150)		(31,150)
Dividends declared - preferred stock	(10,594)						(10,594)	(10,594)		(10,594)
Issuance of common stock and restricted common stock				2	126			128		128
Cancellation of restricted common stock					(109)			(109)		(109)
Exercise of stock options				1	1,309			1,310		1,310
Accrual under deferred compensation arrangements					13			13		13
Amortization of deferred compensation					980			980		980
Distributions to noncontrolling interests		2,133							11,913	11,913
Adjustment for noncontrolling interests					608			608	84	692
Adjustment to record redeemable noncontrolling interests at redemption value		(55)			55			55		55
Redeemable Noncontrolling Partnership Interests [Roll forward]
Net income		1,353
Adjustment for noncontrolling interests		692
Balance, redeemable noncontrolling partnership interests at Mar. 31, 2011		34,252
Balance at Mar. 31, 2011			23	1,483	1,660,001	9,348	(360,951)	1,309,904	221,438	1,531,342
Balance, redeemable noncontrolling partnership interests at Dec. 31, 2011		32,271
Balance at Dec. 31, 2011	1,470,391		23	1,484	1,657,927	3,425	(399,581)	1,263,278	207,113	1,470,391
Net income							(26,049)	26,049	4,269	30,318
Other Comprehensive Income	1,802	14				1,407		1,407	381	1,788
Conversion of operating partnership special common units to shares of common stock									(6,359)	(6,359)
Dividends declared - common stock							(32,700)	(32,700)		(32,700)
Dividends declared - preferred stock	(10,594)						(10,594)	(10,594)		(10,594)
Issuance of common stock and restricted common stock				2	282			284		284
Cancellation of restricted common stock					(247)			(247)		(247)
Exercise of stock options				1	2,337			2,338		2,338
Accrual under deferred compensation arrangements					14			14		14
Amortization of deferred compensation					1,041			1,041		1,041
Distributions to noncontrolling interests		1,893							9,454	9,454
Adjustment for noncontrolling interests					(1,811)			(1,811)	2,654	843
Adjustment to record redeemable noncontrolling interests at redemption value		4,272			(4,272)			(4,272)		(4,272)
Redeemable Noncontrolling Partnership Interests [Roll forward]
Net income		1,089
Adjustment for noncontrolling interests		843
Balance, redeemable noncontrolling partnership interests at Mar. 31, 2012		36,596
Balance at Mar. 31, 2012	$ 1,441,705		$ 23	$ 1,487	$ 1,658,893	$ 4,832	$ (416,826)	$ 1,248,409	$ 193,296	$ 1,441,705