Repurchase Agreements Schedule of Repurchase Agreements by Term, Short or Long (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 9,669,848	$ 5,008,274
Maturity up to One Year [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	9,462,820	5,008,274
Maturity Over One Year [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 207,028	$ 0