CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Total Stockholders' Equity	Common Stock	Additional Paid-In Capital	Cumulative Dividends In Excess Of Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Total
Balance at Dec. 31, 2014	$ 10,735,297	$ 459,746	$ 11,431,987	$ (1,132,541)	$ (23,895)	$ 261,802	$ 10,997,099
Balance (in shares) at Dec. 31, 2014		459,746
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(240,614)			(240,614)		3,111	(237,503)
Other comprehensive income	(4,566)				(4,566)		(4,566)
Issuance of common stock, net	36,812	$ 1,155	35,657			(1,608)	35,204
Issuance of common stock, net (in shares)		1,155
Conversion of DownREIT units to common stock							(1,608)
Repurchase of common stock	(6,096)	$ (128)	(5,968)				(6,096)
Repurchase of common stock (in shares)		(128)
Exercise of stock options	27,221	$ 811	26,410				27,221
Exercise of stock options (in shares)		811
Amortization of deferred compensation	6,165		6,165				6,165
Common dividends ($2.26, $2.18 and $2.10 per share for the year ended 2015, 2014 and 2013, respectively)	(260,686)			(260,686)			(260,686)
Distributions to noncontrolling interests	(263)		(263)			(3,861)	(4,124)
Issuance of noncontrolling interests						2,932	2,932
Balance at Mar. 31, 2015	10,293,270	$ 461,584	11,493,988	(1,633,841)	(28,461)	262,376	10,555,646
Balance (in shares) at Mar. 31, 2015		461,584
Balance at Dec. 31, 2015	9,343,643	$ 465,488	11,647,039	(2,738,414)	(30,470)	402,674	9,746,317
Balance (in shares) at Dec. 31, 2015		465,488
Increase (Decrease) in Stockholders' Equity
Net income (loss)	116,119			116,119		3,626	119,745
Other comprehensive income	(1,203)				(1,203)		(1,203)
Issuance of common stock, net	35,406	$ 1,428	33,978				35,406
Issuance of common stock, net (in shares)		1,428
Conversion of DownREIT units to common stock						(4,136)	(4,136)
Repurchase of common stock	(3,628)	$ (102)	(3,526)				(3,628)
Repurchase of common stock (in shares)		(102)
Exercise of stock options	2,852	$ 111	2,741				2,852
Exercise of stock options (in shares)		111
Amortization of deferred compensation	5,345		5,345				5,345
Common dividends ($2.26, $2.18 and $2.10 per share for the year ended 2015, 2014 and 2013, respectively)	(268,186)			(268,186)			(268,186)
Distributions to noncontrolling interests	(36)		(36)			(4,853)	(4,889)
Issuance of noncontrolling interests						2,200	2,200
Deconsolidation of noncontrolling interests	435			435		67	502
Balance at Mar. 31, 2016	$ 9,230,747	$ 466,925	$ 11,685,541	$ (2,890,046)	$ (31,673)	$ 399,578	$ 9,630,325
Balance (in shares) at Mar. 31, 2016		466,925