Fair Value of Financial Instruments - Fair Value Methodology (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Purchased loans	$ 987,493	$ 1,071,774
Purchases excluded from level 2 fair value	301	496
Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Purchased loans	3,969,944
Discounted cash flow | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Purchased loans	653,523	720,766
Discounted cash flow | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Purchased loans	3,956,992
Liquidation model | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Purchased loans	333,970	351,008
Simple average amount	434	$ 421
Liquidation model | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Purchased loans	$ 12,952
Residential whole loans, at fair value | Level 3 | Liquidation model | Minimum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, annual change in home prices	4.80%	4.50%
Liquidation timeline (in years)	1 month 6 days	1 month 6 days
Fair value inputs, value of underlying property	$ 28	$ 10
Residential whole loans, at fair value | Level 3 | Liquidation model | Minimum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, annual change in home prices	0.00%
Liquidation timeline (in years)	9 months 18 days
Fair value inputs, value of underlying property	$ 60
Residential whole loans, at fair value | Level 3 | Liquidation model | Maximum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, annual change in home prices	20.60%	21.90%
Liquidation timeline (in years)	4 years 6 months	4 years 6 months
Fair value inputs, value of underlying property	$ 4,000	$ 3,995
Residential whole loans, at fair value | Level 3 | Liquidation model | Maximum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, annual change in home prices	15.50%
Liquidation timeline (in years)	4 years 2 months 12 days
Fair value inputs, value of underlying property	$ 3,470
Discount rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Minimum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.024	0.015
Discount rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Minimum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.031
Discount rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Maximum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.097	0.098
Discount rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Maximum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.316
Discount rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Weighted Average | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.050	0.036
Discount rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Weighted Average | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.054
Discount rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Minimum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.067	0.067
Discount rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Minimum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.070
Discount rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Maximum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.500	0.500
Discount rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Maximum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.070
Discount rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Weighted Average | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.079	0.080
Discount rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Weighted Average | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.070
Prepayment rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Minimum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.000	0.000
Prepayment rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Minimum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.000
Prepayment rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Maximum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.403	0.440
Prepayment rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Maximum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.410
Prepayment rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Weighted Average | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.118	0.144
Prepayment rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Weighted Average | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.133
Prepayment rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Weighted Average | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, annual change in home prices	9.60%	9.70%
Prepayment rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Weighted Average | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, annual change in home prices	10.70%
Default rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Minimum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.000	0.000
Default rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Minimum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.000
Default rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Maximum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.524	0.508
Default rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Maximum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.148
Default rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Weighted Average | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.037	0.039
Default rate | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Weighted Average | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.005
Default rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Weighted Average | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidation timeline (in years)	1 year 9 months 18 days	1 year 8 months 12 days
Default rate | Residential whole loans, at fair value | Level 3 | Liquidation model | Weighted Average | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liquidation timeline (in years)	1 year 10 months 24 days
Loss severity | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Minimum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.000	0.000
Loss severity | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Minimum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.000
Loss severity | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Maximum | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	1.000	1.000
Loss severity | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Maximum | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.420
Loss severity | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Weighted Average | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.118	0.117
Loss severity | Residential whole loans, at fair value | Level 3 | Discounted cash flow | Weighted Average | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	0.081
Loss severity | Residential whole loans, at fair value | Level 3 | Liquidation model | Weighted Average | Nonperforming
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, value of underlying property	$ 763	$ 770
Loss severity | Residential whole loans, at fair value | Level 3 | Liquidation model | Weighted Average | Performing
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, value of underlying property	$ 1,590