Condensed Consolidated Statements of Equity (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Series H Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Distributions in Excess of Accumulated Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Total
Balances at Dec. 31, 2011	$ 73,750	$ 3	$ 1,844,611	$ (408,066)	$ (72,771)	$ 116,201	$ 1,553,728
Balances (in shares) at Dec. 31, 2011	2,950,000	33,888,000
Net income	0	0	0	80,123	0	9,827	89,950
Changes in fair value of cash flow hedges and amortization of settlement swaps	0	0	0	0	589	37	626
Changes in fair value of marketable securities	0	0	0	0	(4,267)	(275)	(4,542)
Issuance of common stock under:
Stock option and restricted stock plans	0	0	3,062	0	0	0	3,062
Stock option and restricted stock plans shares (in shares)	0	51,000
Sale of common stock	0	0	268,858	0	0	0	268,858
Sale of common stock (in shares)	0	1,775,000					1,775,748
Equity based compensation costs	0	0	0	0	0	1,678	1,678
Contributions from Noncontrolling Interests	0		0	0	0	2,400	2,400
Distributions to noncontrolling interest	0	0	0	0	0	(12,875)	(12,875)
Redemptions of noncontrolling interest	0	0	0	0	0	(1,595)	(1,595)
Common and preferred stock dividends	0	0	0	(120,199)	0	0	(120,199)
Balances at Sep. 30, 2012	$ 73,750	$ 3	$ 2,116,531	$ (448,142)	$ (76,449)	$ 115,398	$ 1,781,091
Balances (in shares) at Sep. 30, 2012	2,950,000	35,714,000