Organization, Basis of Presentation and Significant Accounting Policies (Details 2) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) community home building $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) community Claim home plaintiff building $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares
Basic and diluted shares outstanding
Weighted average common shares - basic (in shares) | shares	137,580,677	136,918,770	137,326,204	136,852,323
Weighted average DownREIT units outstanding (in shares) | shares	7,500	7,500	7,500	7,500
Effect of dilutive securities (in shares) | shares	584,974	511,463	519,921	550,564
Weighted average common shares - diluted (in shares) | shares	138,173,151	137,437,733	137,853,625	137,410,387
Calculation of Earnings per Share - basic
Net income attributable to common stockholders | $	$ 165,225	$ 197,444	$ 401,100	$ 435,377
Net income allocated to unvested restricted shares | $	(468)	(516)	(1,122)	(1,147)
Net income attributable to common stockholders, adjusted | $	$ 164,757	$ 196,928	$ 399,978	$ 434,230
Weighted average common shares - basic (in shares) | shares	137,580,677	136,918,770	137,326,204	136,852,323
Earnings per common share - basic (in dollars per share) | $ / shares	$ 1.20	$ 1.44	$ 2.91	$ 3.17
Calculation of Earnings per Share - diluted
Net income attributable to common stockholders | $	$ 165,225	$ 197,444	$ 401,100	$ 435,377
Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships | $	10	10	21	20
Adjusted net income attributable to common stockholders | $	$ 165,235	$ 197,454	$ 401,121	$ 435,397
Weighted average common shares - diluted (in shares) | shares	138,173,151	137,437,733	137,853,625	137,410,387
Earnings per common share - diluted (in dollars per share) | $ / shares	$ 1.20	$ 1.44	$ 2.91	$ 3.17
Loss Contingencies [Line Items]
Number of operating apartment communities | community	264		264
Number of apartment homes included in operating apartment communities owned | home	76,158		76,158
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, total class action claims filed number			4
Loss contingency, new claims filed, number			20
Loss contingency, number of plaintiffs | plaintiff			150
Loss contingency, claims filed, number, not consolidated			1
Loss contingency, number of plaintiffs, remaining in class action settlement | plaintiff			2
Loss contingency, claims filed, number, consolidated			19
Loss contingency, new subrogation claims filed, number			5
Loss contingency, subrogation claims filed dismissed, number			1
Loss contingency, subrogation claims filed pending, number			4