Repurchase Agreements (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012 M
Credit Suisse
Repurchase agreements counterparty risk
Amount at Risk	$ 525,370
Weighted Average Months to Maturity for Repurchase Agreements (in months)	2
Counterparty risk as percent of Stockholders' Equity, minimum	19.10%
UBS
Repurchase agreements counterparty risk
Amount at Risk	273,522
Weighted Average Months to Maturity for Repurchase Agreements (in months)	24
Counterparty risk as percent of Stockholders' Equity, minimum	9.90%
UBS AG
Repurchase agreements counterparty risk
Amount at Risk	264,000
UBS Securities LLC
Repurchase agreements counterparty risk
Amount at Risk	9,500
Deutsche Bank Securities, Inc.
Repurchase agreements counterparty risk
Amount at Risk	164,436
Weighted Average Months to Maturity for Repurchase Agreements (in months)	1
Counterparty risk as percent of Stockholders' Equity, minimum	6.00%
Wells Fargo
Repurchase agreements counterparty risk
Amount at Risk	222,298
Weighted Average Months to Maturity for Repurchase Agreements (in months)	21
Counterparty risk as percent of Stockholders' Equity, minimum	8.10%
Wells Fargo Bank
Repurchase agreements counterparty risk
Amount at Risk	144,200
Wells Fargo Securities LLC
Repurchase agreements counterparty risk
Amount at Risk	$ 78,100