Repurchase Agreements - Amounts At Risk (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
[CitigroupMember]
Repurchase Agreement Counterparties With Whom Amount At Risk Exceeds Ten Percent of Stockholders Equity [Line Items]
Amount At Risk	$ 6,259	$ 3,714
Weighted Average Maturity of Repurchase Agreement in Days	28 days	18 days
[SouthStreetMember]
Repurchase Agreement Counterparties With Whom Amount At Risk Exceeds Ten Percent of Stockholders Equity [Line Items]
Amount At Risk		$ 1,802
Weighted Average Maturity of Repurchase Agreement in Days		7 days