Repurchase Agreements Remaining Term to Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 2,321,043	$ 2,437,163
Assets Sold under Agreements to Repurchase, Interest Rate	0.21%	0.34%
WAVG Original Term to Maturity	106	44
Less than 30 days
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 620,942	$ 1,416,608
Assets Sold under Agreements to Repurchase, Interest Rate	0.31%	0.37%
WAVG Original Term to Maturity	51	53
30 to 90 days
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 1,115,526	$ 845,394
Assets Sold under Agreements to Repurchase, Interest Rate	0.19%	0.31%
WAVG Original Term to Maturity	97	35
Maturity90-180DaysMember
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 530,975	$ 175,161
Assets Sold under Agreements to Repurchase, Interest Rate	0.12%	0.22%
WAVG Original Term to Maturity	165	13
Maturity 181 days to 1 year
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Assets Sold under Agreements to Repurchase, Repurchase Liability	$ 53,600
Assets Sold under Agreements to Repurchase, Interest Rate	0.15%
WAVG Original Term to Maturity	364