Summary of Significant Accounting Policies (Details)	3 Months Ended			12 Months Ended
	Mar. 31, 2025 USD ($) real_estate_owned_asset	Mar. 31, 2025 USD ($) real_estate_owned_asset loan	Mar. 31, 2025 USD ($) security_loan real_estate_owned_asset	Dec. 31, 2024 USD ($) real_estate_owned_asset loan	Dec. 31, 2024 USD ($) security_loan real_estate_owned_asset	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restricted cash	$ 0	$ 0	$ 0	$ 0	$ 0
Number of REO assets classified as held for sale investment | real_estate_owned_asset	8	8	8	7	7
Maximum guarantee	$ 3,500,000	$ 3,500,000	$ 3,500,000
Guarantee liability	20,000	20,000	20,000
CECL reserve	741,541,000	$ 741,541,000	$ 741,541,000	$ 733,936,000	$ 733,936,000	$ 751,370,000	$ 576,936,000
Number of loans		138	138	130	130
Principal balance	$ 19,049,712,000	$ 19,049,712,000	$ 19,049,712,000	$ 19,047,518,000	$ 19,047,518,000
Number of properties acquired | real_estate_owned_asset	1	1	1
Level 3 | Minimum | Capitalization rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Measurement input	0.0600	0.0600	0.0600
Level 3 | Minimum | Discount rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Measurement input	0.0700	0.0700	0.0700
Level 3 | Maximum | Capitalization rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Measurement input	0.0800	0.0800	0.0800
Level 3 | Maximum | Discount rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Measurement input	0.1500	0.1500	0.1500
Level 3 | Fair Value, Nonrecurring
Accounts, Notes, Loans and Financing Receivable [Line Items]
CECL reserve	$ 555,400,000	$ 555,400,000	$ 555,400,000
Number of loans | loan		13
Principal balance	$ 1,500,000,000	$ 1,500,000,000	$ 1,500,000,000
Level 3 | Fair Value, Nonrecurring | Minimum | Capitalization rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate owned, measurement input	0.0855	0.0855	0.0855
Level 3 | Fair Value, Nonrecurring | Maximum | Discount rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate owned, measurement input	0.1055	0.1055	0.1055
Building
Accounts, Notes, Loans and Financing Receivable [Line Items]
Estimated useful lives (in years)	40 years
Leasehold Improvements
Accounts, Notes, Loans and Financing Receivable [Line Items]
Estimated useful lives (in years)	10 years
Multifamily Joint Venture
Accounts, Notes, Loans and Financing Receivable [Line Items]
Ownership percentage								85.00%
Multifamily Joint Venture | Walker & Dunlop
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minority participation in senior term facility								15.00%