Condensed Consolidated Statement of Equity (Unaudited) - 9 months ended Sep. 30, 2015 - USD ($) shares in Thousands, $ in Thousands	Total	Series H Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Distributions in Excess of Accumulated Earnings [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]
Balances at Dec. 31, 2014	$ 6,136,068	$ 73,750	$ 6	$ 6,651,165	$ (650,797)	$ (51,452)	$ 113,396
Balances (in shares) at Dec. 31, 2014		2,950	63,683
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	162,477				151,182		11,295
Change in fair value of derivatives and amortization of swap settlements	1,675					1,621	54
Change in fair value of marketable securities	(543)					(526)	(17)
Issuance of common stock under:
Stock option and restricted stock plans	22,173			22,173
Stock option and restricted stock plans (in shares)			170
Sale of common stock	307,835			307,835
Sale of common stock (in shares)			1,382
Equity based compensation costs	5,511			2,564			2,947
Reclassification of noncontrolling interest to redeemable noncontrolling interest	(144)			0			(144)
Changes in the redemption value of redeemable noncontrolling interest	(1,095)			(1,095)			0
Distributions to noncontrolling interest	(16,327)			0			(16,327)
Redemptions of noncontrolling interest	(2,621)			(2,199)			(422)
Common and preferred stock dividends	(283,186)				(283,186)
Balances at Sep. 30, 2015	$ 6,331,823	$ 73,750	$ 6	$ 6,980,443	$ (782,801)	$ (50,357)	$ 110,782
Balances (in shares) at Sep. 30, 2015		2,950	65,235