Repurchase Agreements Repurchase Agreements By Maturity Period (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Deferred Costs	$ 139	$ 243
Maturity up to 30 days [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements, Maturities	369,542	206,112
Maturity 31 to 60 days [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements, Maturities	715,516	492,145
Matuity 61 to 90 days [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements, Maturities	987,579	665,020
Maturity 91 to 120 days [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements, Maturities	545,628	783,371
Maturity 121 to 190 days [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements, Maturities	867,418	1,434,349
Repurchase Agreements [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements, Maturities	$ 3,485,683	$ 3,580,997