CONSOLIDATED STATEMENTS OF EQUITY - USD ($)	Total	Total Stockholders' Equity	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Balance (in shares) at Dec. 31, 2015			154,404,986
Balance at Dec. 31, 2015	$ 5,071,239,000	$ 4,715,414,000	$ 1,544,000	$ 4,926,630,000	$ (212,760,000)		$ 355,825,000
Increase (Decrease) in Stockholders' Equity
Net income	554,839,000	516,995,000			516,995,000		37,844,000
Interest rate cap/swap agreements	0
Amortization of share and unit-based plans (in shares)			139,671
Amortization of share and unit-based plans	40,529,000	40,529,000	$ 2,000	40,527,000
Employee stock purchases (in shares)			28,147
Employee stock purchases	1,697,000	1,697,000		1,697,000
Stock repurchase (in shares)			(11,123,011)
Stock repurchases	(800,018,000)	(800,018,000)	$ (111,000)	(412,391,000)	(387,516,000)
Distributions	(405,501,000)	(405,501,000)			(405,501,000)
Distributions to noncontrolling interests	(35,677,000)						(35,677,000)
Contributions from noncontrolling interests	90,000						90,000
Conversion of noncontrolling interests to common shares (in shares)			535,243
Conversion of noncontrolling interests to common shares	0	12,448,000	$ 5,000	12,443,000			(12,448,000)
Redemption of noncontrolling interests	(30,000)	(23,000)		(23,000)			(7,000)
Adjustment of noncontrolling interests in Operating Partnership	0	24,346,000		24,346,000			(24,346,000)
Balance (in shares) at Dec. 31, 2016			143,985,036
Balance at Dec. 31, 2016	4,427,168,000	4,105,887,000	$ 1,440,000	4,593,229,000	(488,782,000)	$ 0	321,281,000
Increase (Decrease) in Stockholders' Equity
Net income	161,673,000	146,130,000			146,130,000		15,543,000
Interest rate cap/swap agreements	(42,000)	(42,000)				(42,000)
Amortization of share and unit-based plans (in shares)			97,694
Amortization of share and unit-based plans	37,005,000	37,005,000	$ 1,000	37,004,000
Employee stock purchases (in shares)			38,832
Employee stock purchases	1,868,000	1,868,000		1,868,000
Stock repurchase (in shares)			(3,627,390)
Stock repurchases	(221,428,000)	(221,428,000)	$ (36,000)	(135,176,000)	(86,216,000)
Distributions	(407,895,000)	(407,895,000)			(407,895,000)
Distributions to noncontrolling interests	(35,944,000)						(35,944,000)
Contributions from noncontrolling interests	30,000						30,000
Conversion of noncontrolling interests to common shares (in shares)			499,813
Conversion of noncontrolling interests to common shares	0	16,797,000	$ 5,000	16,792,000			(16,797,000)
Redemption of noncontrolling interests	(920,000)	(615,000)		(615,000)			(305,000)
Adjustment of noncontrolling interests in Operating Partnership	$ 0	(2,613,000)		(2,613,000)			2,613,000
Balance (in shares) at Dec. 31, 2017	140,993,985		140,993,985
Balance at Dec. 31, 2017	$ 3,967,999,000	3,681,578,000	$ 1,410,000	4,510,489,000	(830,279,000)	(42,000)	286,421,000
Increase (Decrease) in Stockholders' Equity
Net income	68,972,000	60,020,000			60,020,000		8,952,000
Interest rate cap/swap agreements	(4,424,000)	(4,424,000)				(4,424,000)
Amortization of share and unit-based plans (in shares)			125,723
Amortization of share and unit-based plans	33,551,000	33,551,000	$ 1,000	33,550,000
Exercise of stock options	0
Exercise of stock warrants	0
Employee stock purchases (in shares)			35,293
Employee stock purchases	1,570,000	1,570,000		1,570,000
Stock offerings, net	0
Stock issued to acquire properties	0
Stock repurchases	0
Distributions	(419,239,000)	(419,239,000)			(419,239,000)
Distributions to noncontrolling interests	(34,395,000)						(34,395,000)
Contributions from noncontrolling interests	16,000						16,000
Conversion of noncontrolling interests to common shares (in shares)			66,711
Conversion of noncontrolling interests to common shares	0	75,000	$ 1,000	74,000			(75,000)
Redemption of noncontrolling interests	(759,000)	(511,000)		(511,000)			(248,000)
Adjustment of noncontrolling interests in Operating Partnership	$ 0	22,471,000		22,471,000			(22,471,000)
Balance (in shares) at Dec. 31, 2018	141,221,712		141,221,712
Balance at Dec. 31, 2018	$ 3,188,432,000	$ 2,950,232,000	$ 1,412,000	$ 4,567,643,000	$ (1,614,357,000)	$ (4,466,000)	$ 238,200,000