Commitments and Contingencies (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2011 quarter	Mar. 31, 2011	Dec. 31, 2010
Loss contingencies
Deferred liability recorded and offsetting reduction in additional paid-in capital			$ 27,195,000
Underwriting for initial public offering
Loss contingencies
Amount payable if contingency occurs	18,100,000
Number of prior quarters for calculation of threshold Core Earnings percentage	4
Number of quarters which act as threshold to trigger contingency	24
Threshold percentage of Core Earnings for payment of underwriters' fees (as a percent)	8.00%
Amount paid due to occurrence of contingency		27,195,000
Deferred liability recorded and offsetting reduction in additional paid-in capital			27,195,000
Underwriting fee paid by manager	$ 9,100,000