Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2024 USD ($)	Dec. 31, 2024 USD ($) loan	Dec. 31, 2024 USD ($) security_loan	Dec. 31, 2024 USD ($)	Dec. 31, 2024 USD ($) director	Dec. 31, 2023 USD ($) loan	Dec. 31, 2023 USD ($) security_loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserves for unfunded loan commitments	$ 10,412,000	$ 10,412,000	$ 10,412,000	$ 10,412,000	$ 10,412,000	$ 15,371,000	$ 15,371,000
Number of loans		130	130			178	178
Number of members of board of directors | director					9
Number of non-employee directors eligible for annual compensation | director					7
Number of directors not eligible for compensation | director					2
Board of Directors
Financing Receivable, Allowance for Credit Loss [Line Items]
Annual cash compensation				210,000
Annual cash compensation paid in cash				95,000
Annual cash compensation paid in the form of deferred stock units				115,000
Annual cash compensation				30,000
Audit Committee
Financing Receivable, Allowance for Credit Loss [Line Items]
Annual cash compensation				20,000
Compensation Committee
Financing Receivable, Allowance for Credit Loss [Line Items]
Annual cash compensation				15,000
Corporate Governance Committee
Financing Receivable, Allowance for Credit Loss [Line Items]
Annual cash compensation				10,000
Audit Committee Members
Financing Receivable, Allowance for Credit Loss [Line Items]
Annual cash compensation				10,000
Investment risk management committee
Financing Receivable, Allowance for Credit Loss [Line Items]
Annual cash compensation				7,500
Unfunded Loan Commitment
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserves for unfunded loan commitments	1,263,068,000	$ 1,263,068,000	$ 1,263,068,000	1,263,068,000	$ 1,263,068,000	$ 2,430,664,000	$ 2,430,664,000
Number of loans | loan		60
Aggregate unfunded loan commitments	605,900,000	$ 605,900,000	605,900,000	605,900,000	605,900,000
Net unfunded commitments	$ 657,200,000	$ 657,200,000	$ 657,200,000	$ 657,200,000	$ 657,200,000
Weighted-average future funding period (in years)	2 years 2 months 12 days