Condensed Consolidated Statement of Equity (Unaudited) - 3 months ended Mar. 31, 2016 - 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, 2015	$ 6,337,023	$ 73,750	$ 6	$ 7,003,317	$ (797,329)	$ (42,011)	$ 99,290
Balances (in shares) at Dec. 31, 2015		2,950	65,379
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	86,907				81,836		5,071
Change in fair value of derivatives and amortization of swap settlements	(2,528)					(2,445)	(83)
Change in fair value of marketable securities	317					307	10
Issuance of common stock under:
Stock option and restricted stock plans, net	5,232			5,232
Stock option and restricted stock plans (in shares)			41
Sale of common stock, net	(134)			(134)
Equity based compensation costs	1,490			895			595
Reclassification of Series H preferred stock	(73,750)	$ (73,750)		2,541	(2,541)
Reclassification of Series H preferred stock (in shares)		(2,950)
Changes in the redemption value of redeemable noncontrolling interest	(751)			(841)			90
Distributions to noncontrolling interest	(5,465)						(5,465)
Redemptions of noncontrolling interest	(1,089)			(829)			(260)
Redemptions of noncontrolling interest (in shares)			7
Common and preferred stock dividends	(106,012)				(106,012)
Balances at Mar. 31, 2016	$ 6,241,240	$ 0	$ 6	$ 7,010,181	$ (824,046)	$ (44,149)	$ 99,248
Balances (in shares) at Mar. 31, 2016		0	65,427