Condensed Consolidated Statement of Equity (Unaudited) - 6 months ended Jun. 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]	Accumulated Other Comprehensive Income (Loss) [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	115,295				107,545		7,750
Change in fair value of derivatives and amortization of swap settlements	3,465					3,354	111
Change in fair value of marketable securities	(2,121)					(2,054)	(67)
Issuance of common stock under:
Stock option and restricted stock plans	18,346			18,346
Stock option and restricted stock plans (in shares)			140
Sale of common stock	272,664			272,664
Sale of common stock (in shares)			1,220
Equity based compensation costs	3,457			1,921			1,536
Reclassification of noncontrolling interest to redeemable noncontrolling interest	(144)			0			(144)
Changes in the redemption value of redeemable noncontrolling interest	(384)			(384)			0
Distributions to noncontrolling interest	(11,589)			0			(11,589)
Redemptions of noncontrolling interest	(2,488)			(2,083)			(405)
Common and preferred stock dividends	(187,929)				(187,929)
Balances at Jun. 30, 2015	$ 6,344,640	$ 73,750	$ 6	$ 6,941,629	$ (731,181)	$ (50,152)	$ 110,588
Balances (in shares) at Jun. 30, 2015		2,950	65,043