Short-Term Debt - Mortgage Loans Sold Under Agreement to Repurchase by Counterparty (Details) - Loan Repo Facility $ in Thousands	Mar. 31, 2022 USD ($)
Credit Suisse First Boston Mortgage Capital LLC Tranche Two
Mortgage loans sold under agreement to repurchase
Amount at risk	$ 3,112,276
Credit Suisse First Boston Mortgage Capital LLC Tranche One
Mortgage loans sold under agreement to repurchase
Amount at risk	43,561
Bank of America, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	922,218
JP Morgan Chase Bank
Mortgage loans sold under agreement to repurchase
Amount at risk	207,343
JP Morgan
Mortgage loans sold under agreement to repurchase
Amount at risk	2,757
BNP Paribas
Mortgage loans sold under agreement to repurchase
Amount at risk	3,866
Barclays
Mortgage loans sold under agreement to repurchase
Amount at risk	34,012
Goldman Sachs
Mortgage loans sold under agreement to repurchase
Amount at risk	19,656
Citibank, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	1,043
Morgan Stanley Bank, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	10,214
Royal Bank of Canada
Mortgage loans sold under agreement to repurchase
Amount at risk	14,506
Wells Fargo Bank, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	$ 2,259