Condensed Consolidated Statement of Equity - USD ($) shares in Thousands, $ 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]
Issuance of common stock under:
Cumulative effect upon adoption					$ (2,234)
Cumulative effect upon adoption | ASU 2016-01 [Member]	$ 0			$ 2,234	(2,234)
Cumulative effect upon adoption | ASU 2017-05 [Member]	123,708			119,651		$ 4,057
Balance at period beginning at Dec. 31, 2017	6,396,825	$ 7	$ 7,129,571	(833,726)	(18,446)	119,419
Balances (in shares) at Dec. 31, 2017		66,054
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	96,639			90,918		5,721
Reversal of unrealized gains upon the sale of marketable debt securities	(1)				(1)	0
Change in fair value of derivatives and amortization of swap settlements	6,254				6,046	208
Change in fair value of marketable debt securities, net	(77)				(74)	(3)
Issuance of common stock under:
Stock option and restricted stock plans, net	1,222		1,222
Stock option and restricted stock plans, net (in shares)		7
Sale of common stock, net	(67)		(67)
Sale of common stock, net (in shares)		0
Equity based compensation costs	2,530		2,253			277
Retirement of common stock, net	(3,774)	$ 0	(3,774)
Retirement of common stock, net (in shares)		(17)
Changes in the redemption value of redeemable noncontrolling interest	(1,953)		(1,957)			4
Distributions to noncontrolling interest	(6,297)					(6,297)
Common stock dividends	(122,850)			(122,850)
Balance at period end at Mar. 31, 2018	$ 6,492,159	$ 7	$ 7,127,248	$ (743,773)	$ (14,709)	$ 123,386
Balances (in shares) at Mar. 31, 2018		66,044