Consolidated Statements of Equity - 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 loss, net [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	438,410				414,979		23,431
Reversal of unrealized gains upon the sale of marketable securities	(4,848)					(4,689)	(159)
Change in fair value of derivatives and amortization of swap settlements	15,926					15,403	523
Change in fair value of marketable securities, net	(828)					(801)	(27)
Issuance of common stock under:
Stock option and restricted stock plans, net	18,949			18,949
Stock option and restricted stock plans, net (in shares)			140
Sale of common stock, net	(384)			(384)
Equity based compensation costs	10,899			8,246			2,653
Redemption of Series H preferred stock	(73,750)	$ (73,750)		2,541	(2,541)
Redemption of Series H preferred stock (in shares)		(2,950)
Retirement of common stock, net	(1,045)			(1,045)
Retirement of common stock, net (in shares)			(5)
Changes in the redemption value of redeemable noncontrolling interest	768			172			596
Distributions to noncontrolling interest	(25,854)						(25,854)
Redemptions of noncontrolling interest	(2,511)			(2,117)			(394)
Redemptions of noncontrolling interest (in shares)			14
Preferred stock dividends ($0.45 per share)	(1,314)				(1,314)
Common stock dividends ($6.40 per share)	(419,204)				(419,204)
Balances at Dec. 31, 2016	6,292,237	$ 0	$ 6	7,029,679	(805,409)	(32,098)	100,059
Balances (in shares) at Dec. 31, 2016		0	65,528
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	458,043				433,059		24,984
Reversal of unrealized gains upon the sale of marketable securities	(1,909)					(1,846)	(63)
Change in fair value of derivatives and amortization of swap settlements	12,744					12,322	422
Change in fair value of marketable securities, net	3,284					3,176	108
Issuance of common stock under:
Stock option and restricted stock plans, net	26,635			26,635
Stock option and restricted stock plans, net (in shares)			179
Sale of common stock, net	89,055		$ 1	89,054
Sale of common stock, net (in shares)			345
Equity based compensation costs	11,302			9,529			1,773
Changes in the redemption value of redeemable noncontrolling interest	(65)			(136)			71
Changes in noncontrolling interest from acquisition	22,506						22,506
Distributions to noncontrolling interest	(27,051)						(27,051)
Redemptions of noncontrolling interest	(28,580)			(25,190)			(3,390)
Redemptions of noncontrolling interest (in shares)			2
Common stock dividends ($6.40 per share)	(461,376)				(461,376)
Balances at Dec. 31, 2017	6,396,825	$ 0	$ 7	7,129,571	(833,726)	(18,446)	119,419
Balances (in shares) at Dec. 31, 2017		0	66,054
Issuance of common stock under:
Cumulative adjustment to retained earnings						(2,234)
Cumulative adjustment to retained earnings | ASU 2016-01 [Member]					2,234	(2,234)
Cumulative adjustment to retained earnings | ASU 2017-05 [Member]	123,708				119,651		4,057
Net income	413,599				390,153		23,446
Reversal of unrealized gains upon the sale of marketable securities	13					13	0
Change in fair value of derivatives and amortization of swap settlements	7,824					7,564	260
Change in fair value of marketable securities, net	(118)					(114)	(4)
Stock option and restricted stock plans, net	6,213			6,213
Stock option and restricted stock plans, net (in shares)			41
Sale of common stock, net	(919)			(919)
Equity based compensation costs	12,851			11,651			1,200
Retirement of common stock, net	(51,233)			(51,233)
Retirement of common stock, net (in shares)			(210)
Changes in the redemption value of redeemable noncontrolling interest	(1,164)			(1,143)			(21)
Changes in noncontrolling interest from acquisition	7,919						7,919
Distributions to noncontrolling interest	(29,233)						(29,233)
Redemptions of noncontrolling interest	(1,333)			(1,061)			(272)
Redemptions of noncontrolling interest (in shares)			5
Common stock dividends ($6.40 per share)	(491,108)				(491,108)
Balances at Dec. 31, 2018	$ 6,393,844	$ 0	$ 7	$ 7,093,079	$ (812,796)	$ (13,217)	$ 126,771
Balances (in shares) at Dec. 31, 2018		0	65,890