Fair Value (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Puts item	Dec. 31, 2013 Puts Archstone item	Dec. 31, 2013 Recurring basis Total Fair Value	Dec. 31, 2012 Recurring basis Total Fair Value	Dec. 31, 2013 Recurring basis Total Fair Value Puts	Dec. 31, 2012 Recurring basis Total Fair Value Puts	Dec. 31, 2013 Recurring basis Total Fair Value Interest Rate Caps	Dec. 31, 2012 Recurring basis Total Fair Value Interest Rate Caps	Dec. 31, 2012 Recurring basis Total Fair Value Interest Rate Swaps	Dec. 31, 2013 Recurring basis Quoted Prices in Active Markets for Identical Assets (Level 1)	Dec. 31, 2012 Recurring basis Quoted Prices in Active Markets for Identical Assets (Level 1)	Dec. 31, 2013 Recurring basis Significant Other Observable Inputs (Level 2)	Dec. 31, 2012 Recurring basis Significant Other Observable Inputs (Level 2)	Dec. 31, 2013 Recurring basis Significant Other Observable Inputs (Level 2) Interest Rate Caps	Dec. 31, 2012 Recurring basis Significant Other Observable Inputs (Level 2) Interest Rate Caps	Dec. 31, 2012 Recurring basis Significant Other Observable Inputs (Level 2) Interest Rate Swaps	Dec. 31, 2013 Recurring basis Significant Unobservable Inputs (Level 3)	Dec. 31, 2012 Recurring basis Significant Unobservable Inputs (Level 3)	Dec. 31, 2013 Recurring basis Significant Unobservable Inputs (Level 3) Puts	Dec. 31, 2012 Recurring basis Significant Unobservable Inputs (Level 3) Puts
Financial Instruments Measured/Discussed at Fair Value
Number of ventures in which the entity is required to purchase interest in the investment at guaranteed minimum amount	3	2
Derivative assets							$ 106	$ 19						$ 106	$ 19
Derivative liabilities									(53,484)							(53,484)
Fair value of remaining outstanding Puts					(15,998)	(5,574)													(15,998)	(5,574)
DownREIT units			(887)	(1,017)						(887)	(1,017)
Indebtedness			(6,294,848)	(4,077,397)						(2,657,143)	(2,102,927)	(3,637,705)	(1,974,470)
Total			$ (6,311,627)	$ (4,137,453)						$ (2,658,030)	$ (2,103,944)	$ (3,637,599)	$ (2,027,935)				$ (15,998)	$ (5,574)