Commitments and Contingencies - Additional Information (Detail)	6 Months Ended					12 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2025 USD ($) loan	Jun. 30, 2025 USD ($) security_loan	Jun. 30, 2025 USD ($)	Jun. 30, 2025 USD ($) director	Dec. 31, 2024 USD ($) loan	Dec. 31, 2024 USD ($) security_loan	Jun. 30, 2024 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Current expected credit loss reserves for unfunded loan commitments	$ 11,713,000	$ 11,713,000	$ 11,713,000	$ 11,713,000	$ 11,713,000	$ 10,412,000	$ 10,412,000	$ 9,900,000
Number of loans		144	144			130	130
Number of non-employee directors eligible for annual compensation | director					6
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	1,412,084,000	$ 1,412,084,000	$ 1,412,084,000	1,412,084,000	$ 1,412,084,000	$ 1,263,068,000	$ 1,263,068,000
Number of loans | loan		58
Aggregate unfunded loan commitments	666,100,000	$ 666,100,000	666,100,000	666,100,000	666,100,000
Net unfunded commitments	$ 746,000,000	$ 746,000,000	$ 746,000,000	$ 746,000,000	$ 746,000,000
Weighted-average future funding period (in years)	2 years 7 months 6 days