Condensed Consolidated Statements of Stockholders' Equity, Noncontrolling Interest, and Comprehensive Income (Unaudited) (USD $) In Thousands, except Share data	Total	Series Preferred stock	Series H Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Distributions in Excess of Net Income [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
Balance at Dec. 31, 2010	$ 1,355,014	$ 25,000	$ 0	$ 3	$ 1,515,468	$ (313,308)	$ (77,217)	$ 205,068
Balance (in shares) at Dec. 31, 2010		1,000,000		31,325,000
Comprehensive income:
Net income	39,648	0	0	0	0	31,766	0	7,882
Reversal of unrealized gains upon the sale of marketable securites	(4,402)	0	0	0	0	0	(4,109)	(293)
Change in fair value of cash flow hedges and amortization of swap settlements	6,917	0	0	0	0	0	6,469	448
Change in fair value of marketable securities	(398)	0	0	0	0	0	(380)	(18)
Comprehensive income (loss)	41,765
Issuance of common stock under:
Stock option and restricted stock plans	7,591	0	0	0	7,591	0	0	0
Stock option and restricted stock plans (in shares)				97,000
Sale of common stock	256,790	0	0	0	256,790	0	0	0
Sale of common stock (in shares)	1,959,411			1,960,000
Equity based compensation costs	804	0	0	0	0	0	0	804
Equity related issuance costs	(828)	0	0	0	(828)	0	0	0
Issuance of Series H Preferred	71,209	0	73,750	0	(2,541)	0	0	0
Issuance of Series H Preferred (in shares)			2,950,000
Redemption of Series F Preferred	(25,000)	(25,000)	0	0	0	0	0	0
Redemption of Series F Preferred (in shares)		(1,000,000)
Contributions from noncontrolling interest	800	0	0		0	0	0	800
Distributions to noncontrolling interest	(13,268)	0	0	0	0	0	0	(13,268)
Dividends declared	(105,210)	0	0	0	0	(105,210)	0	0
Redemption of Series B Preferred	(78,800)	0	0	0	1,200	0	0	(80,000)
Redemptions of noncontrolling interest	(4,644)	0	0	0	(1,134)	0	0	(3,510)
Balance at Sep. 30, 2011	$ 1,506,223	$ 0	$ 73,750	$ 3	$ 1,776,546	$ (386,752)	$ (75,237)	$ 117,913
Balance (in shares) at Sep. 30, 2011			2,950,000	33,382,000