Archstone Acquisition (Details 2) (USD $)	12 Months Ended	0 Months Ended
	Dec. 31, 2013 item	Feb. 27, 2013 Archstone community	Feb. 27, 2013 Archstone Archstone Legacy Entities entity community	Dec. 31, 2013 Archstone Archstone Legacy Entities
Investments in Archstone Consolidated Entities
Percentage of assets and liabilities acquired		40.00%
Number of operating communities in which Archstone Legacy Entities holds indirect interest			16
Number of operating communities acquired		54
Aggregate liquidation preference				$ 90,000,000
Number of entities previously entered into tax protection arrangements			1
Percentage of the economic cost of preferred redemption obligations			40.00%
Economic cost of preferred redemption obligations fair value, proportionate share of entity				$ 37,000,000
Investments in Archstone Unconsolidated Entities
Number of joint ventures	3