Fair Value of Financial Instruments - Valuation Techniques And Unobservable Inputs Applied (Details) - Level 3 $ in Thousands	Jun. 30, 2020 USD ($)
Securitized mortgage borrowings | DCF
Valuation techniques
Estimated fair value of liabilities	$ (2,213,863)
Securitized mortgage borrowings | Measurement Input, Default Rate | DCF | Minimum
Unobservable input
Measurement input, securitized mortgage borrowings	0.02
Securitized mortgage borrowings | Measurement Input, Default Rate | DCF | Maximum
Unobservable input
Measurement input, securitized mortgage borrowings	24.0
Securitized mortgage borrowings | Measurement Input, Default Rate | DCF | Weighted Average
Unobservable input
Measurement input, securitized mortgage borrowings	2.5
Securitized mortgage borrowings | Measurement Input, Loss Severity | DCF | Minimum
Unobservable input
Measurement input, securitized mortgage borrowings	0.13
Securitized mortgage borrowings | Measurement Input, Loss Severity | DCF | Maximum
Unobservable input
Measurement input, securitized mortgage borrowings	98.9
Securitized mortgage borrowings | Measurement Input, Loss Severity | DCF | Weighted Average
Unobservable input
Measurement input, securitized mortgage borrowings	63.5
Securitized mortgage borrowings | Measurement Input, Discount Rate | DCF | Minimum
Unobservable input
Measurement input, securitized mortgage borrowings	2.8
Securitized mortgage borrowings | Measurement Input, Discount Rate | DCF | Maximum
Unobservable input
Measurement input, securitized mortgage borrowings	25.0
Securitized mortgage borrowings | Measurement Input, Discount Rate | DCF | Weighted Average
Unobservable input
Measurement input, securitized mortgage borrowings	4.2
Long-term debt | DCF
Valuation techniques
Estimated fair value of liabilities	$ (41,811)
Long-term debt | Measurement Input, Discount Rate | DCF
Unobservable input
Measurement input, long-term debt	8.4
Long-term debt | Measurement Input, Discount Rate | DCF | Weighted Average
Unobservable input
Measurement input, long-term debt	8.4
Securitized mortgage collateral | DCF
Valuation techniques
Estimated fair value of assets	$ 2,225,422
Securitized mortgage collateral | Measurement Input, Prepayment Rate | DCF | Minimum
Unobservable input
Measurement input, securitized mortgage collateral	4.5
Securitized mortgage collateral | Measurement Input, Prepayment Rate | DCF | Maximum
Unobservable input
Measurement input, securitized mortgage collateral	33.8
Securitized mortgage collateral | Measurement Input, Prepayment Rate | DCF | Weighted Average
Unobservable input
Measurement input, securitized mortgage collateral	10.3
Mortgage servicing rights | DCF
Valuation techniques
Estimated fair value of assets	$ 279
Mortgage servicing rights | Measurement Input Inactive Bid | Market pricing
Unobservable input
Measurement input, mortgage servicing rights	100
Mortgage servicing rights | Measurement Input Inactive Bid | Market pricing | Weighted Average
Unobservable input
Measurement input, mortgage servicing rights	100
Interest rate lock commitments. net (IRLCs) | Market pricing
Valuation techniques
Estimated fair value of assets	$ 1,799
Interest rate lock commitments. net (IRLCs) | Measurement Input, Pull-through Rate | Market pricing | Minimum
Unobservable input
Measurement input, derivative assets - IRLCs, net	22.9
Interest rate lock commitments. net (IRLCs) | Measurement Input, Pull-through Rate | Market pricing | Maximum
Unobservable input
Measurement input, derivative assets - IRLCs, net	96.2
Interest rate lock commitments. net (IRLCs) | Measurement Input, Pull-through Rate | Market pricing | Weighted Average
Unobservable input
Measurement input, derivative assets - IRLCs, net	69.0