Fair Value (Details 2) (Recurring basis, USD $) In Thousands, unless otherwise specified	Jun. 30, 2014
Total Fair Value
Financial Instruments Measured/Discussed at Fair Value
DownREIT units	$ (1,067)
Indebtedness	(6,195,397)
Total	(6,210,933)
Total Fair Value | Puts
Financial Instruments Measured/Discussed at Fair Value
Fair value of remaining outstanding Puts	(14,582)
Total Fair Value | Interest Rate Caps
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	14
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Instruments Measured/Discussed at Fair Value
DownREIT units	(1,067)
Indebtedness	(3,607,341)
Total	(3,608,408)
Significant Other Observable Inputs (Level 2)
Financial Instruments Measured/Discussed at Fair Value
Indebtedness	(2,588,056)
Total	(2,587,943)
Significant Other Observable Inputs (Level 2) | Interest Rate Caps
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	14
Significant Unobservable Inputs (Level 3)
Financial Instruments Measured/Discussed at Fair Value
Total	(14,582)
Significant Unobservable Inputs (Level 3) | Puts
Financial Instruments Measured/Discussed at Fair Value
Fair value of remaining outstanding Puts	(14,582)
Cash Flow Hedges | Total Fair Value | Interest Rate Caps
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	99
Cash Flow Hedges | Significant Other Observable Inputs (Level 2) | Interest Rate Caps
Financial Instruments Measured/Discussed at Fair Value
Derivative assets	$ 99