Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2024 USD ($) real_estate_owned_asset	Dec. 31, 2024 USD ($) real_estate_owned_asset loan	Dec. 31, 2024 USD ($) real_estate_owned_asset security_loan	Dec. 31, 2023 USD ($) loan	Dec. 31, 2023 USD ($) security_loan	Dec. 31, 2022 USD ($)	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restricted cash	$ 0	$ 0	$ 0	$ 0	$ 0
Borrower escrows	$ 482,200,000	$ 482,200,000	$ 482,200,000	640,600,000	640,600,000
Number of REO assets classified as held for sale investment | real_estate_owned_asset	7	7	7
Maximum guarantee	$ 3,500,000	$ 3,500,000	$ 3,500,000
Guarantee liability	20,000	20,000	20,000	0	0
CECL reserve	733,936,000	$ 733,936,000	$ 733,936,000	$ 576,936,000	$ 576,936,000	$ 326,137,000
Number of loans		130	130	178	178
Principal balance	$ 19,047,518,000	$ 19,047,518,000	$ 19,047,518,000	$ 23,787,012,000	$ 23,787,012,000	$ 25,017,880,000
Number of properties acquired | real_estate_owned_asset	7	7	7
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	0.0772	0.0772	0.0772
Level 3 | Maximum | Capitalization rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Measurement input	0.0855	0.0855	0.0855
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	$ 580,700,000	$ 580,700,000	$ 580,700,000
Number of loans | loan		13
Principal balance	$ 1,800,000,000	$ 1,800,000,000	$ 1,800,000,000
Level 3 | Fair Value, Nonrecurring | Minimum | Capitalization rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate owned, measurement input	0.0600	0.0600	0.0600
Level 3 | Fair Value, Nonrecurring | Minimum | Discount rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate owned, measurement input	0.0750	0.0750	0.0750
Level 3 | Fair Value, Nonrecurring | Maximum | Capitalization rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate owned, measurement input	0.0800	0.0800	0.0800
Level 3 | Fair Value, Nonrecurring | Maximum | Discount rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate owned, measurement input	0.1000	0.1000	0.1000
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%