Organization, Basis of Presentation and Significant Accounting Policies (Details 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic and diluted shares outstanding
Weighted average common shares - basic (in shares)	140,450,744		139,113,390		140,413,857	138,724,479
Weighted average DownREIT units outstanding (in shares)	7,500		7,500		7,500	7,500
Effect of dilutive securities (in shares)	279,916		497,341		330,974	495,397
Weighted average common shares - diluted (in shares)	140,738,160		139,618,231		140,752,331	139,227,376
Calculation of Earnings per Share - basic
Net income attributable to common stockholders	$ 170,828	$ 167,971	$ 168,281	$ 170,366	$ 338,799	$ 338,647
Net income allocated to unvested restricted shares	(390)		(435)		(817)	(935)
Net income attributable to common stockholders, adjusted	$ 170,438		$ 167,846		$ 337,982	$ 337,712
Weighted average common shares - basic (in shares)	140,450,744		139,113,390		140,413,857	138,724,479
Earnings per common share - basic (in dollars per share)	$ 1.21		$ 1.21		$ 2.41	$ 2.43
Calculation of Earnings per Share - diluted
Net income attributable to common stockholders	$ 170,828	$ 167,971	$ 168,281	$ 170,366	$ 338,799	$ 338,647
Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships	12		12		24	23
Adjusted net income attributable to common stockholders	$ 170,840		$ 168,293		$ 338,823	$ 338,670
Weighted average common shares - diluted (in shares)	140,738,160		139,618,231		140,752,331	139,227,376
Earnings per common share - diluted (in dollars per share)	$ 1.21		$ 1.21		$ 2.41	$ 2.43