Short-Term Debt - Mortgage Loans Sold Under Agreement to Repurchase by Counterparty (Details) - Loan Repo Facility $ in Thousands	Sep. 30, 2024 USD ($)
Atlas Securitized Products, L.P., Goldman Sachs Bank USA, Nomura Corporate Funding Americas and Mizuho Bank, Ltd
Mortgage loans sold under agreement to repurchase
Amount at risk	$ 4,965,381
Royal Bank of Canada
Mortgage loans sold under agreement to repurchase
Amount at risk	144,170
Bank of America, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	131,432
Atlas Securitized Products, L.P.
Mortgage loans sold under agreement to repurchase
Amount at risk	86,753
BNP Paribas
Mortgage loans sold under agreement to repurchase
Amount at risk	68,995
Barclays Capital
Mortgage loans sold under agreement to repurchase
Amount at risk	51,364
Citibank, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	26,294
Wells Fargo Bank, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	24,140
Morgan Stanley Bank, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	12,327
Goldman Sachs
Mortgage loans sold under agreement to repurchase
Amount at risk	10,536
JPMorgan Chase Bank, N.A.
Mortgage loans sold under agreement to repurchase
Amount at risk	$ 33,726