Borrowings (Schedule of Debt Repayments) (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Debt Instrument [Line Items]
Expected principal repayments related to consolidated residential mortgage loan securitizations	$ 782,400
Repurchase Agreements
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	2,497,601
Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two	75,442
2020 Scheduled Repayment of Principal	0
2021 Scheduled Repayment of Principal	0
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	0
Total Scheduled Repayment of Principal	2,573,043
Other Secured Borrowings
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	385,620
Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two	239,332
2020 Scheduled Repayment of Principal	175,047
2021 Scheduled Repayment of Principal	155,582
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	127,954
Total Scheduled Repayment of Principal	1,083,535
Senior Notes
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	0
Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two	0
2020 Scheduled Repayment of Principal	0
2021 Scheduled Repayment of Principal	210,000
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	0
Total Scheduled Repayment of Principal	210,000
Total
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	4,223,519
Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two	1,238,863
2020 Scheduled Repayment of Principal	1,041,201
2021 Scheduled Repayment of Principal	1,205,890
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	950,312
Total Scheduled Repayment of Principal	8,659,785
HMBS-related obligations
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	1,340,298
Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two	924,089
2020 Scheduled Repayment of Principal	866,154
2021 Scheduled Repayment of Principal	840,308
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	822,358
Total Scheduled Repayment of Principal	$ 4,793,207