Consolidated Statements of Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Preferred Shares Series B	Preferred Shares Series C	Preferred Shares Series D	Preferred Shares Series E	Cumulative Preferred Distributions	Common Shares	Cumulative Common Distributions	Additional Paid in Capital	Cumulative Net Income	Cumulative Other Comprehensive Income (Loss)	Comprehensive Income (Loss)
Balance at Dec. 31, 2008	$ 2,921,112	$ 169,079	$ 145,015	$ 368,270	$ 0	$ (331,928)	$ 569	$ (2,441,841)	$ 2,939,694	$ 2,072,254
Balance (in shares) at Dec. 31, 2008		7,000,000	6,000,000	15,180,000			56,932,985
Comprehensive income (loss):
Net income	164,674									164,674		164,674
Unrealized gain (loss) on derivative instrument	2,547										2,547	2,547
Total comprehensive income	167,221											167,221
Issuance of shares, net	9								9
Issuance of shares, net (in shares)							326
Repurchase and retirement of common shares	(14,486)						(10)		(14,476)
Repurchase and retirement of common shares (in shares)							(1,012,500)
Stock grants	619						1		618
Stock grants (in shares)							44,250
Distributions	(185,409)					(50,668)		(134,741)
Balance at Dec. 31, 2009	2,889,066	169,079	145,015	368,270		(382,596)	560	(2,576,582)	2,925,845	2,236,928	2,547
Balance (in shares) at Dec. 31, 2009		7,000,000	6,000,000	15,180,000			55,965,061
Comprehensive income (loss):
Net income	135,409									135,409		135,409
Unrealized gain (loss) on derivative instrument	(9,501)										(9,501)	(9,501)
Unrealized income on investment in available for sale securities	19										19	19
Foreign currency translation adjustments	11,641										11,641	11,641
Total comprehensive income	137,568											137,568
Issuance of shares, net	430,778						161		430,617
Issuance of shares, net (in shares)							16,125,000
Redemption of shares	(175,000)	(169,079)							(5,921)
Redemption of shares (in shares)		(7,000,000)
Stock grants	896								896
Stock grants (in shares)							48,625
Distributions	(149,030)					(49,656)		(99,374)
Purchase of noncontrolling equity interest	(2,588)								(2,588)
Balance at Dec. 31, 2010	3,131,690		145,015	368,270	0	(432,252)	721	(2,675,956)	3,348,849	2,372,337	4,706
Balance (in shares) at Dec. 31, 2010			6,000,000	15,180,000			72,138,686
Comprehensive income (loss):
Net income	109,984									109,984		109,984
Unrealized gain (loss) on derivative instrument	(8,840)										(8,840)	(8,840)
Realized gain on investment in available for sale securities	(19)										(19)	(19)
Foreign currency translation adjustments	(632)										(632)	(632)
Increase in share of investees other comprehensive income	76										76	76
Total comprehensive income	100,569											100,569
Issuance of shares, net	529,698				265,391		115		264,192
Issuance of shares, net (in shares)					11,000,000		11,500,000
Stock grants	1,039						1		1,038
Stock grants (in shares)							83,050
Distributions	(194,479)					(44,405)		(150,074)
Balance at Dec. 31, 2011	$ 3,568,517		$ 145,015	$ 368,270	$ 265,391	$ (476,657)	$ 837	$ (2,826,030)	$ 3,614,079	$ 2,482,321	$ (4,709)
Balance (in shares) at Dec. 31, 2011			6,000,000	15,180,000	11,000,000		83,721,736