Consolidated Statement Of Shareholders' Equity - USD ($) $ in Thousands	Total	downREIT OP units	5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 392,878 and 399,896 shares issued and outstanding, respectively	Preferred Shares	Preferred Shares 5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 392,878 and 399,896 shares issued and outstanding, respectively	Common Shares	Common Shares downREIT OP units	Common Shares 5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 392,878 and 399,896 shares issued and outstanding, respectively	Additional Paid-in Capital	Additional Paid-in Capital downREIT OP units	Additional Paid-in Capital 5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 392,878 and 399,896 shares issued and outstanding, respectively	Accumulated Dividends in Excess of Net Income	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest	Noncontrolling Interest downREIT OP units
Beginning balance (in shares) at Dec. 31, 2020				405,896		76,727,394
Beginning balance at Dec. 31, 2020	$ 2,548,747			$ 159,997		$ 771			$ 3,297,305			$ (988,272)	$ (5,644)	$ 84,590
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding amounts attributable to redeemable noncontrolling interests	148,867											146,562		2,305
Other comprehensive income - change in fair value of interest rate swaps, excluding portion attributable to redeemable noncontrolling interests	2,918												2,918
Dividends declared to common shareholders	(248,000)											(248,000)
Dividends declared to preferred shareholders	(6,031)											(6,031)
Distributions declared to noncontrolling interests, excluding amounts attributable to redeemable noncontrolling interests	(3,282)													(3,282)
Common shares issued, net (in shares)						847,528
Common shares issued, net	87,066					$ 9			87,057
Shares issued under dividend reinvestment plan (in shares)						15,710
Shares issued under dividend reinvestment plan	1,507								1,507
Share-based compensation expense, net of forfeitures (in shares)						163,092
Share-based compensation expense, net of forfeitures	10,874					$ 2			10,872
Shares withheld for employee taxes (in shares)						(28,563)
Shares withheld for employee taxes	(2,939)								(2,939)
Conversion and redemption of downREIT OP units (in Shares)							49,484
Conversion and redemption of downREIT OP units							$ 0			$ 5,049
Conversion and redemption of downREIT OP units		$ (99)													$ (5,148)
Contributions from noncontrolling interests	6,554													6,554
Ending balance (in shares) at Sep. 30, 2021				405,896		77,774,645
Ending balance at Sep. 30, 2021	2,546,182			$ 159,997		$ 782			3,398,851			(1,095,741)	(2,726)	85,019
Beginning balance (in shares) at Jun. 30, 2021				405,896		77,760,588
Beginning balance at Jun. 30, 2021	2,575,839			$ 159,997		$ 782			3,395,189			(1,062,641)	(3,238)	85,750
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding amounts attributable to redeemable noncontrolling interests	52,946											52,122		824
Other comprehensive income - change in fair value of interest rate swaps, excluding portion attributable to redeemable noncontrolling interests	512												512
Dividends declared to common shareholders	(83,212)											(83,212)
Dividends declared to preferred shareholders	(2,010)											(2,010)
Distributions declared to noncontrolling interests, excluding amounts attributable to redeemable noncontrolling interests	(1,555)													(1,555)
Common shares issued, net (in shares)						19
Common shares issued, net	(67)					$ 0			(67)
Shares issued under dividend reinvestment plan (in shares)						4,194
Shares issued under dividend reinvestment plan	488								488
Share-based compensation expense, net of forfeitures (in shares)						10,907
Share-based compensation expense, net of forfeitures	3,367					$ 0			3,367
Shares withheld for employee taxes (in shares)						(1,063)
Shares withheld for employee taxes	(126)								(126)
Ending balance (in shares) at Sep. 30, 2021				405,896		77,774,645
Ending balance at Sep. 30, 2021	2,546,182			$ 159,997		$ 782			3,398,851			(1,095,741)	(2,726)	85,019
Beginning balance (in shares) at Dec. 31, 2021				405,896		78,603,305
Beginning balance at Dec. 31, 2021	2,663,148			$ 159,997		$ 790			3,488,794			(1,066,932)	(2,047)	82,546
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding amounts attributable to redeemable noncontrolling interests	272,668											269,798		2,870
Other comprehensive income - change in fair value of interest rate swaps, excluding portion attributable to redeemable noncontrolling interests	8,131												8,131
Dividends declared to common shareholders	(256,867)											(256,867)
Dividends declared to preferred shareholders	(6,026)											(6,026)
Distributions declared to noncontrolling interests, excluding amounts attributable to redeemable noncontrolling interests	(4,066)													(4,066)
Common shares issued, net (in shares)						2,500,569
Common shares issued, net	292,344					$ 25			292,319
Exercise of stock options (in shares)						366
Exercise of stock options	35								35
Shares issued under dividend reinvestment plan (in shares)						13,832
Shares issued under dividend reinvestment plan	1,584								1,584
Share-based compensation expense, net of forfeitures (in shares)						110,915
Share-based compensation expense, net of forfeitures	11,258					$ 2			11,256
Shares withheld for employee taxes (in shares)						(40,974)
Shares withheld for employee taxes	(4,886)								(4,886)
Conversion of preferred shares (in shares)					(7,018)
Conversion of preferred shares					$ (175)
Conversion of preferred shares (in shares)								1,675
Conversion of preferred shares			$ 0								$ 175
Conversion and redemption of downREIT OP units (in Shares)							14,598
Conversion and redemption of downREIT OP units		$ 0					$ 0			$ 1,385
Conversion and redemption of downREIT OP units															$ (1,385)
Deconsolidation of VIE	972													972
Adjustment to redeemable noncontrolling interests	3,585								3,585
Ending balance (in shares) at Sep. 30, 2022				398,878		81,204,286
Ending balance at Sep. 30, 2022	2,981,880			$ 159,822		$ 817			3,794,247			(1,060,027)	6,084	80,937
Beginning balance (in shares) at Jun. 30, 2022				398,878		80,896,804
Beginning balance at Jun. 30, 2022	2,876,427			$ 159,822		$ 813			3,758,161			(1,126,463)	3,550	80,544
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding amounts attributable to redeemable noncontrolling interests	157,000											156,138		862
Other comprehensive income - change in fair value of interest rate swaps, excluding portion attributable to redeemable noncontrolling interests	2,534												2,534
Dividends declared to common shareholders	(87,694)											(87,694)
Dividends declared to preferred shareholders	(2,008)											(2,008)
Distributions declared to noncontrolling interests, excluding amounts attributable to redeemable noncontrolling interests	(1,441)													(1,441)
Common shares issued, net (in shares)						296,872
Common shares issued, net	32,892					$ 3			32,889
Exercise of stock options (in shares)						366
Exercise of stock options	35								35
Shares issued under dividend reinvestment plan (in shares)						5,832
Shares issued under dividend reinvestment plan	573								573
Share-based compensation expense, net of forfeitures (in shares)						6,810
Share-based compensation expense, net of forfeitures	3,579					$ 1			3,578
Shares withheld for employee taxes (in shares)						(2,398)
Shares withheld for employee taxes	(248)								(248)
Deconsolidation of VIE	972													972
Adjustment to redeemable noncontrolling interests	(741)								(741)
Ending balance (in shares) at Sep. 30, 2022				398,878		81,204,286
Ending balance at Sep. 30, 2022	$ 2,981,880			$ 159,822		$ 817			$ 3,794,247			$ (1,060,027)	$ 6,084	$ 80,937