Earnings Per Common Share - Narrative (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive potential common shares - forward equity agreements (in shares)	0	0	0	808,000
Dilutive potential common shares - DownREIT conversions (in shares)	5,501,000	0	0	0
Common shares attributable to DownREIT conversions, total (in shares)	7,000,000
Down REIT
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares of anti-dilutive securities excluded from earnings per share calculation (in shares)		7,000,000	7,000,000	7,000,000