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	95,921											94,440		1,481
Other comprehensive income (loss) - change in fair value of interest rate swaps, excluding portion attributable to redeemable noncontrolling interests	2,406												2,406
Dividends declared to common shareholders	(164,788)											(164,788)
Dividends declared to preferred shareholders	(4,021)											(4,021)
Distributions declared to noncontrolling interests, excluding amounts attributable to redeemable noncontrolling interests	(1,727)													(1,727)
Common shares issued, net (in shares)						847,509
Common shares issued, net	87,133					$ 9			87,124
Shares issued under dividend reinvestment plan (in shares)						11,516
Shares issued under dividend reinvestment plan	1,019								1,019
Share-based compensation expense, net of forfeitures (in shares)						152,185
Share-based compensation expense, net of forfeitures	7,507					$ 2			7,505
Shares withheld for employee taxes (in shares)						(27,500)
Shares withheld for employee taxes	(2,813)								(2,813)
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 Jun. 30, 2021				405,896		77,760,588
Ending balance at Jun. 30, 2021	2,575,839			$ 159,997		$ 782			3,395,189			(1,062,641)	(3,238)	85,750
Beginning balance (in shares) at Mar. 31, 2021				405,896		77,706,466
Beginning balance at Mar. 31, 2021	2,604,960			$ 159,997		$ 781			3,386,917			(1,024,417)	(2,300)	83,982
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding amounts attributable to redeemable noncontrolling interests	46,990											46,204		786
Other comprehensive income (loss) - change in fair value of interest rate swaps, excluding portion attributable to redeemable noncontrolling interests	(938)												(938)
Dividends declared to common shareholders	(82,417)											(82,417)
Dividends declared to preferred shareholders	(2,011)											(2,011)
Distributions declared to noncontrolling interests, excluding amounts attributable to redeemable noncontrolling interests	(943)													(943)
Common shares issued, net (in shares)						16
Common shares issued, net	(81)					$ 1			(82)
Shares issued under dividend reinvestment plan (in shares)						5,236
Shares issued under dividend reinvestment plan	474								474
Share-based compensation expense, net of forfeitures (in shares)						4,473
Share-based compensation expense, net of forfeitures	3,358					$ 0			3,358
Shares withheld for employee taxes (in shares)						(71)
Shares withheld for employee taxes	(8)								(8)
Conversion and redemption of downREIT OP units (in Shares)							44,468
Conversion and redemption of downREIT OP units							$ 0			4,530
Conversion and redemption of downREIT OP units		(99)													(4,629)
Contributions from noncontrolling interests	6,554													6,554
Ending balance (in shares) at Jun. 30, 2021				405,896		77,760,588
Ending balance at Jun. 30, 2021	2,575,839			$ 159,997		$ 782			3,395,189			(1,062,641)	(3,238)	85,750
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	115,668											113,660		2,008
Other comprehensive income (loss) - change in fair value of interest rate swaps, excluding portion attributable to redeemable noncontrolling interests	5,597												5,597
Dividends declared to common shareholders	(169,173)											(169,173)
Dividends declared to preferred shareholders	(4,018)											(4,018)
Distributions declared to noncontrolling interests, excluding amounts attributable to redeemable noncontrolling interests	(2,625)													(2,625)
Common shares issued, net (in shares)						2,203,697
Common shares issued, net	259,452					$ 22			259,430
Shares issued under dividend reinvestment plan (in shares)						8,000
Shares issued under dividend reinvestment plan	1,011								1,011
Share-based compensation expense, net of forfeitures (in shares)						104,105
Share-based compensation expense, net of forfeitures	7,679					$ 1			7,678
Shares withheld for employee taxes (in shares)						(38,576)
Shares withheld for employee taxes	(4,638)								(4,638)
Conversion of preferred shares (in shares)					(7,018)
Conversion of preferred shares (in shares)								1,675
Conversion of preferred shares					$ (175)
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)
Adjustment to redeemable noncontrolling interests	4,326								4,326
Ending balance (in shares) at Jun. 30, 2022				398,878		80,896,804
Ending balance at Jun. 30, 2022	2,876,427			$ 159,822		$ 813			3,758,161			(1,126,463)	3,550	80,544
Beginning balance (in shares) at Mar. 31, 2022				405,896		79,417,472
Beginning balance at Mar. 31, 2022	2,714,577			$ 159,997		$ 799			3,572,591			(1,101,154)	1,525	80,819
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income, excluding amounts attributable to redeemable noncontrolling interests	62,675											61,676		999
Other comprehensive income (loss) - change in fair value of interest rate swaps, excluding portion attributable to redeemable noncontrolling interests	2,025												2,025
Dividends declared to common shareholders	(84,977)											(84,977)
Dividends declared to preferred shareholders	(2,008)											(2,008)
Distributions declared to noncontrolling interests, excluding amounts attributable to redeemable noncontrolling interests	(866)													(866)
Common shares issued, net (in shares)						1,473,928
Common shares issued, net	176,703					$ 14			176,689
Shares issued under dividend reinvestment plan (in shares)						4,230
Shares issued under dividend reinvestment plan	509								509
Share-based compensation expense, net of forfeitures (in shares)						(4,786)
Share-based compensation expense, net of forfeitures	3,500					$ 0			3,500
Shares withheld for employee taxes (in shares)						(306)
Shares withheld for employee taxes	(37)								(37)
Conversion of preferred shares (in shares)					(7,018)
Conversion of preferred shares (in shares)								1,675
Conversion of preferred shares					$ (175)
Conversion of preferred shares			$ 0								$ 175
Conversion and redemption of downREIT OP units (in Shares)							4,591
Conversion and redemption of downREIT OP units		$ 0					$ 0			$ 408
Conversion and redemption of downREIT OP units															$ (408)
Adjustment to redeemable noncontrolling interests	4,326								4,326
Ending balance (in shares) at Jun. 30, 2022				398,878		80,896,804
Ending balance at Jun. 30, 2022	$ 2,876,427			$ 159,822		$ 813			$ 3,758,161			$ (1,126,463)	$ 3,550	$ 80,544