CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental disclosures of non-cash investing and financing activities
Stock issued in connection with stock grants (in shares)	157,779	115,163
Common stock issued through the dividend reinvestment plan (in shares)	2,142	2,434	2,002
Common stock issued through the dividend reinvestment plan	$ 372,000	$ 335,000	$ 269,000
Number of shares withheld to satisfy employees' tax withholding and other liabilities	45,090	55,523	48,310
Shares withheld to satisfy employees' tax withholding and other liabilities, value	$ 5,979,000	$ 4,746,000	$ 6,127,000
Number of shares forfeited	1,529	7,970	7,653
Shares cancelled upon forfeiture	$ 726,000	$ 2,938,000	$ 1,105,000
Common stock dividends declared but not paid	171,257,000	153,207,000	138,476,000
Change in redemption value of redeemable noncontrolling interest	(965,000)	(3,709,000)	1,246,000
Unrealized loss on cash flow hedges	5,354,000	(121,000)	0
Cash flow hedge losses reclassified to earnings	5,774,000	6,237,000	59,376,000
Casualty (gain) loss and impairment loss, net	(10,542,000)	0	0
Capital Leased Assets, Gross	39,019,000	31,784,000
Noncontrolling interests derecognition		(17,816,000)
Stock issued in connection with stock grants, value			$ 16,019,000
Number of options granted for common stock			215,230
Options granted for common stock, value			$ 5,768,000
Cash flow hedge losses reclassified to interest expense, net			5,892,000
Reclassification adjustment on derivatives to loss on interest rate contract			$ 53,484,000
(Decrease) increase in redeemable noncontrolling interests	$ 2,053,000	$ 3,709,000
Restricted Stock Converted From Performance Shares [Member]
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares)	95,826	16,209
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Granted (in shares)	61,953	98,954	123,977
Fair value of shares issued	$ 10,720,000	$ 12,799,000
Archstone Enterprise LP
Supplemental disclosures of non-cash investing and financing activities
Number of shares of common stock issued as partial consideration for acquisition			14,889,706
Value of shares of common stock issued as partial consideration for acquisition			$ 1,875,210,000
Increase in redeemable noncontrolling interests associated with business acquisition			13,262,000
Assumed principal amount of indebtedness			3,512,202,000
Obligation related to outstanding preferred interests			67,500,000
Accumulated earnings less dividends
Supplemental disclosures of non-cash investing and financing activities
Change in redemption value of redeemable noncontrolling interest			1,246,000
Accumulated other comprehensive loss
Supplemental disclosures of non-cash investing and financing activities
Unrealized loss on cash flow hedges	5,354,000	(121,000)
Cash flow hedge losses reclassified to earnings	$ 5,774,000	$ 6,237,000	$ 59,376,000
Deferred Compensation, Share-based Payments [Member] | Non Employee Director [Member]
Supplemental disclosures of non-cash investing and financing activities
Conversion of restricted stock units (in shares)	46,589
Fair value of shares issued	$ 3,552,000
Avalon at Edgewater [Member]
Supplemental disclosures of non-cash investing and financing activities
Casualty (gain) loss and impairment loss, net	(15,538,000)
Avalon Bloomfield Station
Supplemental disclosures of non-cash investing and financing activities
Capital Leased Assets, Gross	3,299,000
New England [Member]
Supplemental disclosures of non-cash investing and financing activities
Casualty (gain) loss and impairment loss, net	4,195,000
New England [Member] | Avalon at Edgewater [Member]
Supplemental disclosures of non-cash investing and financing activities
Casualty (gain) loss and impairment loss, net	$ 26,039,000