Repurchase Agreements - Amounts At Risk (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 [NomuraMember]	Dec. 31, 2012 [CitigroupMember]	Dec. 31, 2012 [SouthStreetMember]
Repurchase Agreement Counterparties With Whom Amount At Risk Exceeds Ten Percent of Stockholders Equity [Line Items]
Amount At Risk	$ 2,100	$ 3,714	$ 1,802
Weighted Average Maturity of Repurchase Agreement in Days	30 days	18 days	7 days