Condensed Consolidated Statements of Equity (Unaudited) (USD $) In Thousands, 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 Loss, Net [Member]	Noncontrolling Interest [Member]	Total
Balances at Dec. 31, 2012	$ 73,750	$ 3	$ 2,204,778	$ (444,466)	$ (69,261)	$ 115,312	$ 1,880,116
Balances (in shares) at Dec. 31, 2012	2,950	36,443
Net income	0	0	0	123,041	0	12,112	135,153
Reversal of unrealized gains upon the sale of marketable securities	0	0	0	0	(1,673)	(94)	(1,767)
Change in fair value of cash flow hedges and amortization of swap settlements	0	0	0	0	9,439	537	9,976
Changes in fair value of marketable securities	0	0	0	0	(1,094)	(62)	(1,156)
Issuance of common stock under:
Stock option and restricted stock plans	0	0	6,411	0	0	0	6,411
Stock option and restricted stock plans shares (in shares)	0	63
Sale of common stock	0	0	122,905	0	0	0	122,905
Sale of common stock (in shares)	0	817
Equity based compensation costs	0	0	(759)	0	0	1,626	867
Distributions to noncontrolling interest	0	0	0	0	0	(14,108)	(14,108)
Redemptions of noncontrolling interest	0	0	(3,294)	0	0	(1,819)	(5,113)
Common and preferred stock dividends	0	0	0	(139,580)	0	0	(139,580)
Balances at Sep. 30, 2013	$ 73,750	$ 3	$ 2,330,041	$ (461,005)	$ (62,589)	$ 113,504	$ 1,993,704
Balances (in shares) at Sep. 30, 2013	2,950	37,323