Commitments and Contingencies - Additional Information (Detail)		6 Months Ended
	Apr. 30, 2021 USD ($)	Jun. 30, 2021 USD ($) Directors Loans
Commitments And Contingencies [Line Items]
Number of loans receivable | Loans		86
Number of independent directors entitled to annual compensation | Directors		5
Loans Receivable [Member]
Commitments And Contingencies [Line Items]
Unfunded loan commitments		$ 3,400,000,000
Average Rate		74.40%
Aggregate unfunded loan commitments		$ 2,400,000,000
Weighted-average future funding period		3 years 1 month 6 days
Five Independent Board of Directors [Member]
Commitments And Contingencies [Line Items]
Annual cash compensation	$ 175,000	$ 175,000
Annual cash compensation paid in the form of deferred stock units		100,000
Annual cash compensation paid in cash		75,000
Five Independent Board of Directors [Member] | Amendment One [Member]
Commitments And Contingencies [Line Items]
Annual cash compensation	210,000
Annual cash compensation paid in the form of deferred stock units	115,000
Annual cash compensation paid in cash	95,000
Chairperson of Audit Committee [Member]
Commitments And Contingencies [Line Items]
Annual cash compensation		20,000
Audit Committee Members [Member]
Commitments And Contingencies [Line Items]
Annual cash compensation		10,000
Compensation and Corporate Governance Committees [Member]
Commitments And Contingencies [Line Items]
Annual cash compensation	10,000	$ 10,000
Compensation and Corporate Governance Committees [Member] | Amendment One [Member]
Commitments And Contingencies [Line Items]
Annual cash compensation	15,000
Investment risk management committee [Member]
Commitments And Contingencies [Line Items]
Annual cash compensation	$ 7,500