Organization, Basis of Presentation and Significant Accounting Policies (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic and diluted shares outstanding
Weighted average common shares - basic	129,208,839	97,044,603	126,057,793	95,742,676
Weighted average DownREIT units outstanding (in shares)	7,500	7,500	7,500	7,500
Effect of dilutive securities (in shares)		494,466	411,821	651,382
Weighted average common shares - diluted	129,216,339	97,546,569	126,477,114	96,401,558
Calculation of Earnings per Share - basic
Net (loss) income attributable to common stockholders	$ (10,715)	$ 86,844	$ 100,929	$ 301,512
Net loss (income) allocated to unvested restricted shares	16	(186)	(166)	(1,003)
Net (loss) income attributable to common stockholders, adjusted	(10,699)	86,658	100,763	300,509
Weighted average common shares - basic	129,208,839	97,044,603	126,057,793	95,742,676
(Loss) earnings per common share - basic (in dollars per share)	$ (0.08)	$ 0.89	$ 0.80	$ 3.14
Calculation of Earnings per Share - diluted
Net (loss) income attributable to common stockholders	(10,715)	86,844	100,929	301,512
Add: noncontrolling interests of DownREIT unitholders in consolidated partnerships, including discontinued operations	8	7	24	21
Adjusted net (loss) income attributable to common stockholders	$ (10,707)	$ 86,851	$ 100,953	$ 301,533
Weighted average common shares - diluted	129,216,339	97,546,569	126,477,114	96,401,558
(Loss) earnings per common share - diluted (in dollars per share)	$ (0.08)	$ 0.89	$ 0.80	$ 3.13
Options to purchase shares of common stock excluded from computation of earnings per share amount (in shares)			605,899	418,177
Estimated forfeiture rate of stock options (as a percent)			1.20%