Condensed Consolidated Statement of Equity - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Distributions in Excess of Accumulated Earnings [Member]	Accumulated Other Comprehensive Loss, Net [Member]	Noncontrolling Interest [Member]
Balance at period beginning at Dec. 31, 2016	$ 6,292,237	$ 6	$ 7,029,679	$ (805,409)	$ (32,098)	$ 100,059
Balances (in shares) at Dec. 31, 2016		65,528,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	348,381			329,446		18,935
Reversal of unrealized gains upon the sale of marketable securities	(1,650)				(1,596)	(54)
Change in fair value of derivatives and amortization of swap settlements	7,405				7,160	245
Change in fair value of marketable securities, net	1,966				1,902	64
Issuance of common stock under:
Stock option and restricted stock plans, net	24,079		24,079
Stock option and restricted stock plans, net (in shares)		160,000
Sale of common stock, net	$ 80,377		80,377
Sale of common stock, net (in shares)	311,873	312,000
Equity based compensation costs	$ 4,894		3,814			1,080
Changes in the redemption value of redeemable noncontrolling interest	(903)		(916)			13
Contributions from noncontrolling interest	22,506					22,506
Distributions to noncontrolling interest	(21,072)					(21,072)
Redemptions of noncontrolling interest	(28,557)		(25,167)			(3,390)
Redemptions of noncontrolling interest (in shares)		2,000
Common stock dividends	(345,769)			(345,769)
Balance at period end at Sep. 30, 2017	$ 6,383,894	$ 6	$ 7,111,866	$ (821,732)	$ (24,632)	$ 118,386
Balances (in shares) at Sep. 30, 2017		66,002,000