Stockholders' Equity (Details) (USD $)	12 Months Ended					1 Months Ended	12 Months Ended	26 Months Ended	1 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Archstone Enterprise LP	Dec. 31, 2012 CEP II and CEP III	Nov. 30, 2010 CEP II	Dec. 31, 2012 CEP II	Dec. 31, 2012 CEP II	Aug. 31, 2012 CEP III	Dec. 31, 2012 CEP III
Equity
Common stock, shares authorized	140,000,000	140,000,000
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock shares issued				16,675,000	18,840,206		1,435,215	3,925,980		729,991
Common stock shares issued in connection with stock options exercised	407,784
Common stock shares issued through dividend reinvestment plan	2,331	3,343	5,687
Common stock shares issued in connection with stock grants	96,592	511,817	102,984
Number of shares of stock grants withheld	121,351	129,762	48,882
Restricted common stock shares forfeited	4,027
Common stock shares issued for Employee Stock Purchase Plan	6,260
Options of common stock granted to employees (in shares)	115,303
Common stock shares issued, offer price (in dollars per share)				$ 130.00
Net proceeds from common stock shares issued	$ 2,414,775,000	$ 1,035,302,000	$ 380,973,000	$ 2,102,718,000
Maximum value of shares of common stock that can be sold (in dollars)						500,000,000			750,000,000
Period during which common stock can be sold						36 months			36 months
Percentage of compensation received by sales agent										1.50%
Shares sold, average sales price (in dollars per share)							$ 140.41	$ 127.36		$ 142.09
Net proceeds from sales of shares (in dollars)	$ 2,430,190,000	$ 1,049,835,000	$ 381,365,000				$ 198,489,000	$ 492,490,000		$ 102,168,000