Loans Held for Investment and Loans Held for Investment at Fair Value - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Accounts Notes And Loans Receivable [Line Items]
Accured interest on loan	$ 17,793,000	$ 17,793,000		$ 13,295,000
Financing receivable, 90 days or more past due, still accruing	$ 123,988,000	123,988,000		$ 0
Accrued interest income recognized on nonaccrual loans		0	$ 0
Cash basis interest income recognized on nonaccrual loans		6,700,000	5,400,000
Average recorded investment of individually evaluated loans, computed using month-end balances		180,200,000	$ 105,200,000
90+days
Accounts Notes And Loans Receivable [Line Items]
Annualized charge rate of non performing loans	0.10%			0.52%
Cares Act
Accounts Notes And Loans Receivable [Line Items]
Loans held for investment	$ 293,700,000	293,700,000
Accured interest on loan	11,600,000	11,600,000
COVID-19
Accounts Notes And Loans Receivable [Line Items]
Loans	$ 293,700,000	$ 293,700,000