Repurchase Agreements Repurchase Agreements, Term to Original Maturity (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount	$ 3,150,254	$ 3,580,754
Deferred Costs	0	(243)
Maturity up to 30 days [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount	574,164	4,736
Maturity 30 to 90 Days [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount	566,959	1,176,631
Maturity 91 to 180 days [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount	1,514,454	1,439,225
Maturity 181 days up to 1 year [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount	329,232	960,405
Maturity 1 year or longer [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount	$ 165,445	$ 0