Schedule of ARM Securities Forward Purchase Commitments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Schedule Of Investment Income Reported Amounts By Category [Line Items]
Forward purchase agreements - Face	$ 70,000	$ 0
Forward purchase agreements - Cost	71,839	0
Forward purchase agreements - Fair Value	72,040	0
Forward purchase agreements - Net Asset	$ 201	$ 0