Variable Interest Entities - VIE Income Statement (Details) ([VariableInterestEntityPrimaryBeneficiaryMember], USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
[VariableInterestEntityPrimaryBeneficiaryMember]
Portfolio Income [Abstract]
Interest income	$ 2,429	$ 3,460
Interest expense	322	459
Net interest income	2,107	3,001
Unrealized gains on mortgage-backed securities	(9,130)	(8,618)
Realized gains on mortgage-backed securities	(923)	(824)
Losses on Eurodollar futures	6,852	6,368
Net portfolio income	(1,094)	(73)
Selling General And Administrative Expense [Abstract]
Directors' fees and liability insurance	83	124
Audit, legal and other professional fees	106	152
Direct REIT operating expenses	36	74
Other administrative	41	53
Total expenses	266	403
Net income	$ (1,360)	$ (476)