Schedule of ARM Securities Forward Purchase Commitments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Forward purchase agreements - Face		$ 565,000
Forward purchase agreements - Cost		585,100
Forward purchase agreements - Fair Market Value		587,247
Forward purchase agreements - Net Asset		$ 2,147