Fair Value - Significant Unobservable Inputs (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities	$ 91,941	$ 93,806
Domestic servicing rights	23,143	22,390
VIE assets	62,163,347	62,556,497
VIE liabilities	55,006,596	55,363,025
Primary Beneficiary
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Woodstar Fund investments	2,065,498	2,073,533
VIE assets	63,800
VIE liabilities	100
Fair value measurements on recurring basis | Loans under fair value option
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	2,446,636	2,516,008
Fair value measurements on recurring basis | RMBS
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities	91,941	93,806
Fair value measurements on recurring basis | CMBS
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities	31,299	27,345
Fair value measurements on recurring basis | Woodstar Fund investments
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Woodstar Fund investments	2,065,498	2,073,533
Fair value measurements on recurring basis | Domestic servicing rights
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Domestic servicing rights	23,143	22,390
Fair value measurements on recurring basis | VIE assets | Primary Beneficiary
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE assets	37,470,618	38,937,576
Fair value measurements on recurring basis | VIE liabilities | Primary Beneficiary
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE liabilities	35,901,085	37,288,545
Fair value measurements on recurring basis | Level III | Loans under fair value option
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	$ 2,446,636	$ 2,516,008
Fair value measurements on recurring basis | Level III | Loans under fair value option | Minimum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option, duration	3 years	3 years 3 months 18 days
Fair value measurements on recurring basis | Level III | Loans under fair value option | Minimum | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	0.028	0.028
Fair value measurements on recurring basis | Level III | Loans under fair value option | Minimum | FICO score
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	585	585
Fair value measurements on recurring basis | Level III | Loans under fair value option | Minimum | LTV
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	0.04	0.04
Fair value measurements on recurring basis | Level III | Loans under fair value option | Minimum | Purchase price
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	0.800	0.800
Fair value measurements on recurring basis | Level III | Loans under fair value option | Maximum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option, duration	37 years 3 months 18 days	37 years 6 months
Fair value measurements on recurring basis | Level III | Loans under fair value option | Maximum | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	0.105	0.105
Fair value measurements on recurring basis | Level III | Loans under fair value option | Maximum | FICO score
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	829	829
Fair value measurements on recurring basis | Level III | Loans under fair value option | Maximum | LTV
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	0.92	0.93
Fair value measurements on recurring basis | Level III | Loans under fair value option | Maximum | Purchase price
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	1.068	1.068
Fair value measurements on recurring basis | Level III | Loans under fair value option | Weighted-average
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option, duration	26 years	25 years 10 months 24 days
Fair value measurements on recurring basis | Level III | Loans under fair value option | Weighted-average | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	0.045	0.046
Fair value measurements on recurring basis | Level III | Loans under fair value option | Weighted-average | FICO score
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	750	750
Fair value measurements on recurring basis | Level III | Loans under fair value option | Weighted-average | LTV
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	0.64	0.64
Fair value measurements on recurring basis | Level III | Loans under fair value option | Weighted-average | Purchase price
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loans under fair value option	1.013	1.013
Fair value measurements on recurring basis | Level III | RMBS
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities	$ 91,941	$ 93,806
Loss severity for specified percentage of portfolio (as a percent)	3.00%	3.00%
Fair value measurements on recurring basis | Level III | RMBS | Minimum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loss severity for specified percentage of portfolio (as a percent)	45.00%	45.00%
Fair value measurements on recurring basis | Level III | RMBS | Minimum | Constant prepayment rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.021	0.022
Fair value measurements on recurring basis | Level III | RMBS | Minimum | Constant default rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.009	0.008
Fair value measurements on recurring basis | Level III | RMBS | Minimum | Loss severity
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0	0
Fair value measurements on recurring basis | Level III | RMBS | Minimum | Delinquency rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.08	0.08
Fair value measurements on recurring basis | Level III | RMBS | Minimum | Servicer advances
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.18	0.22
Fair value measurements on recurring basis | Level III | RMBS | Maximum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Loss severity for specified percentage of portfolio (as a percent)	80.00%	80.00%
Fair value measurements on recurring basis | Level III | RMBS | Maximum | Constant prepayment rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.091	0.092
Fair value measurements on recurring basis | Level III | RMBS | Maximum | Constant default rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.033	0.033
Fair value measurements on recurring basis | Level III | RMBS | Maximum | Loss severity
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.50	0.62
Fair value measurements on recurring basis | Level III | RMBS | Maximum | Delinquency rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.25	0.25
Fair value measurements on recurring basis | Level III | RMBS | Maximum | Servicer advances
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.76	0.78
Fair value measurements on recurring basis | Level III | RMBS | Weighted-average | Constant prepayment rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.045	0.045
Fair value measurements on recurring basis | Level III | RMBS | Weighted-average | Constant default rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.016	0.016
Fair value measurements on recurring basis | Level III | RMBS | Weighted-average | Loss severity
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.12	0.13
Fair value measurements on recurring basis | Level III | RMBS | Weighted-average | Delinquency rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.14	0.13
Fair value measurements on recurring basis | Level III | RMBS | Weighted-average | Servicer advances
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.47	0.51
Fair value measurements on recurring basis | Level III | CMBS
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities	$ 27,271	$ 27,345
Fair value measurements on recurring basis | Level III | CMBS | Minimum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
CMBS, term	0 years	0 years
Fair value measurements on recurring basis | Level III | CMBS | Minimum | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0	0
Fair value measurements on recurring basis | Level III | CMBS | Maximum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
CMBS, term	5 years 7 months 6 days	6 years 8 months 12 days
Fair value measurements on recurring basis | Level III | CMBS | Maximum | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.592	0.585
Fair value measurements on recurring basis | Level III | CMBS | Weighted-average
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
CMBS, term	1 year 8 months 12 days	2 years 2 months 12 days
Fair value measurements on recurring basis | Level III | CMBS | Weighted-average | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.131	0.126
Fair value measurements on recurring basis | Level III | Woodstar Fund investments
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Woodstar Fund investments	$ 2,065,498	$ 2,073,533
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Direct capitalization rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.0443
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Implied capitalization rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input		0.0443
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Minimum | Discount rate - properties
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input		0.065
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Minimum | Discount rate - debt
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.030	0.030
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Minimum | Terminal capitalization rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input		0.048
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Maximum | Discount rate - properties
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input		0.073
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Maximum | Discount rate - debt
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.062	0.064
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Maximum | Terminal capitalization rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input		0.055
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Weighted-average | Discount rate - properties
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input		0.070
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Weighted-average | Discount rate - debt
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.046	0.047
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Weighted-average | Terminal capitalization rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input		0.052
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Weighted-average | Direct capitalization rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input	0.0443
Fair value measurements on recurring basis | Level III | Woodstar Fund investments | Weighted-average | Implied capitalization rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Available-for-sale securities, measurement input		0.0443
Fair value measurements on recurring basis | Level III | Domestic servicing rights
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Domestic servicing rights	$ 23,143	$ 22,390
Fair value measurements on recurring basis | Level III | Domestic servicing rights | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Domestic servicing rights	0.0875	0.0850
Fair value measurements on recurring basis | Level III | Domestic servicing rights | Discount rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Domestic servicing rights	0.15	0.15
Fair value measurements on recurring basis | Level III | Domestic servicing rights | Weighted-average | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Domestic servicing rights	0.0875	0.0850
Fair value measurements on recurring basis | Level III | Domestic servicing rights | Weighted-average | Discount rate
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
Domestic servicing rights	0.15	0.15
Fair value measurements on recurring basis | Level III | VIE assets | Minimum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE duration (in years)	0 years	0 years
Fair value measurements on recurring basis | Level III | VIE assets | Minimum | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE assets	0	0
Fair value measurements on recurring basis | Level III | VIE assets | Maximum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE duration (in years)	8 years 8 months 12 days	9 years
Fair value measurements on recurring basis | Level III | VIE assets | Maximum | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE assets	8.625	7.531
Fair value measurements on recurring basis | Level III | VIE assets | Weighted-average
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE duration (in years)	2 years	2 years 7 months 6 days
Fair value measurements on recurring basis | Level III | VIE assets | Weighted-average | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE assets	0.228	0.264
Fair value measurements on recurring basis | Level III | VIE assets | Primary Beneficiary
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE assets	$ 37,470,618	$ 38,937,576
Fair value measurements on recurring basis | Level III | VIE liabilities | Minimum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE duration (in years)	0 years	0 years
Fair value measurements on recurring basis | Level III | VIE liabilities | Minimum | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE liabilities	0	0
Fair value measurements on recurring basis | Level III | VIE liabilities | Maximum
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE duration (in years)	8 years 8 months 12 days	9 years
Fair value measurements on recurring basis | Level III | VIE liabilities | Maximum | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE liabilities	8.625	7.531
Fair value measurements on recurring basis | Level III | VIE liabilities | Weighted-average
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE duration (in years)	2 years 4 months 24 days	2 years
Fair value measurements on recurring basis | Level III | VIE liabilities | Weighted-average | Debt yield
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE liabilities	0.119	0.171
Fair value measurements on recurring basis | Level III | VIE liabilities | Primary Beneficiary
Quantitative information for Level 3 Fair Value Measurements for assets and liabilities measured at fair value on recurring basis
VIE liabilities	$ 3,981,624	$ 5,514,152