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 Loss, Net [Member]	Noncontrolling Interest [Member]	Total
Balances at Dec. 31, 2013	$ 73,750	$ 4	$ 2,345,763	$ (474,426)	$ (60,472)	$ 113,619	$ 1,998,238
Balances (in shares) at Dec. 31, 2013	2,950,000	37,421,000
Net income	0	0	0	23,280	0	3,126	26,406
Reversal of unrealized gains upon the sale of marketable securities	0	0	0	0	(402)	(25)	(427)
Change in fair value of cash flow hedges and amortization of swap settlements	0	0	0	0	2,565	155	2,720
Changes in fair value of marketable securities	0	0	0	0	1,914	116	2,030
Issuance of common stock under:
Stock option and restricted stock plans	0	0	1,769	0	0	0	1,769
Stock option and restricted stock plans shares (in shares)	0	13,000
Equity distribution agreement	0	0	157,596	0	0	0	157,596
Equity distribution agreement (in shares)	0	958,000					0
Equity based compensation costs	0	0	(125)	0	0	673	548
Contributions from noncontrolling interest	0	0	0	0	0	1,419,816	1,419,816
Distributions to noncontrolling interest	0	0	0	0	0	(3,969)	(3,969)
Redemptions of noncontrolling interest	0	0	0	0	0	(101)	(101)
Common and preferred stock dividends	0	0	0	(47,222)	0	0	(47,222)
Balances at Mar. 31, 2014	$ 73,750	$ 4	$ 2,505,003	$ (498,368)	$ (56,395)	$ 1,533,410	$ 3,557,404
Balances (in shares) at Mar. 31, 2014	2,950,000	38,392,000