Equity (Details 2) (USD $)	0 Months Ended	3 Months Ended				1 Months Ended	3 Months Ended
	Feb. 27, 2013	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Minimum Lehman Brothers Holdings, Inc	Mar. 31, 2013 Archstone Lehman Brothers Holdings, Inc	Aug. 31, 2012 CEP III	Mar. 31, 2013 CEP III
Equity
Common stock shares issued in connection with stock options exercised		3,531
Common stock shares issued through dividend reinvestment plan		550	735
Common stock shares issued in connection with stock grants		119,292	91,471
Number of shares of stock grants withheld		29,219	39,054
Restricted common stock shares forfeited		5,214
Number of shares issued	14,889,706	14,889,706			14,889,706
Ownership percentage of common stock considered as restriction to acquire additional forms of ownership				5.00%
Options of common stock granted to employees (in shares)		215,230
Maximum value of shares of common stock that can be sold (in dollars)						$ 750,000,000
Period during which common stock can be sold						36 months
Additional shares authorized for issuance							646,274,000
Common stock shares issued							0