Organization, Basis of Presentation and Significant Accounting Policies (Details 2) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) community home building $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2018 USD ($) community Claim home plaintiff building $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares
Basic and diluted shares outstanding
Weighted average common shares - basic (in shares) | shares	137,840,045	137,580,677	137,802,461	137,326,204
Weighted average DownREIT units outstanding (in shares) | shares	7,500	7,500	7,500	7,500
Effect of dilutive securities (in shares) | shares	367,465	584,974	374,334	519,921
Weighted average common shares - diluted (in shares) | shares	138,215,010	138,173,151	138,184,295	137,853,625
Calculation of Earnings per Share - basic
Net income attributable to common stockholders | $	$ 254,662	$ 165,225	$ 396,305	$ 401,100
Net income allocated to unvested restricted shares | $	(727)	(468)	(1,167)	(1,122)
Net income attributable to common stockholders, adjusted | $	$ 253,935	$ 164,757	$ 395,138	$ 399,978
Weighted average common shares - basic (in shares) | shares	137,840,045	137,580,677	137,802,461	137,326,204
Earnings per common share - basic (in dollars per share) | $ / shares	$ 1.84	$ 1.20	$ 2.87	$ 2.91
Calculation of Earnings per Share - diluted
Net income attributable to common stockholders | $	$ 254,662	$ 165,225	$ 396,305	$ 401,100
Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships | $	11	10	22	21
Adjusted net income attributable to common stockholders | $	$ 254,673	$ 165,235	$ 396,327	$ 401,121
Weighted average common shares - diluted (in shares) | shares	138,215,010	138,173,151	138,184,295	137,853,625
Earnings per common share - diluted (in dollars per share) | $ / shares	$ 1.84	$ 1.20	$ 2.87	$ 2.91
Loss Contingencies [Line Items]
Number of operating apartment communities | community	268		268
Number of apartment homes included in operating apartment communities owned | home	77,995		77,995
Avalon at Edgewater
Loss Contingencies [Line Items]
Number of operating apartment communities | building	2		2
Number of operating apartment communities, uninhabitable | building	1		1
Number of units in operating apartment communities, uninhabitable | home	240		240
Number of apartment homes included in operating apartment communities owned | home	168		168
Loss contingency, new class action claims filed number			3
Loss contingency class action claims filed, number of apartments included in settlement			66
Loss Contingency Class Action Claims Filed, Number of Apartments Included in Settlement Submitted			44
Loss Contingency Class Action Claims Filed, Number of Apartments Included in Settlement Submitted Amount | $			$ 6,900
Loss Contingency Class Action Claims Filed, Number of Apartments Issued Awards By Claims Adjuster			25
Loss Contingency Class Action Claims Filed, Timing Remaining for Claim Evaluation			2 months
Loss contingency, total class action claims filed number			4
Loss contingency, claims filed, number, consolidated			18
Loss contingency, new claims filed, number			19
Loss contingency, number of plaintiffs | plaintiff			143
Loss Contingency Class Action Claims Filed, Number of Apartments in Settlement Resolved			50
Loss Contingency Class Action Claims Filed, Number of Apartments in Settlement Previously Resolved			10
Loss Contingency Subrogation Claims Filed Pending Not Dismissed Number			1
Loss Contingency Class Action Claims Filed, Number of Apartments Included in Settlement Remaining			1
Loss contingency, new subrogation claims filed, number			7
Loss contingency, subrogation claims filed dismissed, number			1
Loss Contingency Subrogation Claims Filed Resolved Number			2
Loss contingency, subrogation claims filed pending, number			4