Repurchase Agreements Remaining Term to Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Balance	$ 4,752,348	$ 3,267,984
Assets Sold under Agreements to Repurchase, Interest Rate	2.01%	2.69%
WAVG Original Term to Maturity	45	66
Less than 30 days
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Balance	$ 2,078,185	$ 2,319,911
Assets Sold under Agreements to Repurchase, Interest Rate	2.12%	2.74%
WAVG Original Term to Maturity	34	56
30 to 90 days
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Balance	$ 2,674,163	$ 948,073
Assets Sold under Agreements to Repurchase, Interest Rate	1.93%	2.55%
WAVG Original Term to Maturity	52	89