Borrowings (Schedule of Debt Repayments) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2018
Debt Instrument [Line Items]
Expected principal repayments related to consolidated residential mortgage loan securitizations	$ 778,100
Repurchase Agreements
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	1,402,683
Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two	94,248
2019 Scheduled Repayment of Principal		$ 1,358,542
2020 Scheduled Repayment of Principal	0	78,530
2021 Scheduled Repayment of Principal	0	61,776
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	0	0
Total Scheduled Repayment of Principal	1,496,931	1,498,848
Long-term Debt, Maturities, Repayments of Principal after Year Five		0
Other Secured Borrowings
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	370,933
Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two	236,976
2019 Scheduled Repayment of Principal		194,135
2020 Scheduled Repayment of Principal	221,269	205,198
2021 Scheduled Repayment of Principal	0	13,150
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	0	0
Total Scheduled Repayment of Principal	829,178	412,483
Long-term Debt, Maturities, Repayments of Principal after Year Five		0
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	86,000
2019 Scheduled Repayment of Principal		0
2020 Scheduled Repayment of Principal	0	0
2021 Scheduled Repayment of Principal	0	0
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	0	86,000
Total Scheduled Repayment of Principal	86,000	86,000
Long-term Debt, Maturities, Repayments of Principal after Year Five		0
Total
Debt Instrument [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Rolling Twelve Months	1,773,616
Long-term Debt, Maturities, Repayments of Principal in Rolling Year Two	417,224
2019 Scheduled Repayment of Principal		1,552,677
2020 Scheduled Repayment of Principal	221,269	283,728
2021 Scheduled Repayment of Principal	0	74,926
Long-term Debt, Maturities, Repayments of Principal in Rolling after Year Five	0	86,000
Total Scheduled Repayment of Principal	$ 2,412,109	1,997,331
Long-term Debt, Maturities, Repayments of Principal after Year Five		$ 0

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Total amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing.

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