Loans Held for Investment - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Receivables [Abstract]
Loans renegotiated in troubled debt restructurings	$ 7,200,000		$ 7,200,000		$ 14,500,000
Troubled restructurings included in non-accrual loans	5,000,000.0		5,000,000.0		11,300,000
Loans renegotiated in troubled debt restructurings, accrual loans	2,200,000		2,200,000		3,200,000
Financing receivable, after allowance for credit loss, noncurrent	200,000		200,000		2,900,000
TDR commitment to lend					$ 0
Troubled debt restructurings	0		0
Charge-offs directly related to modifying troubled debt restructurings	0	$ 0	0	$ 0
Balance of defaulted loans under trouble debt restructurings	0		0
Impaired financing receivable, recorded investment	67,400,000		67,400,000
Commitments to purchase or sell	0	0	0	0
Proceeds from sale of loans held-for-investment	$ 0	$ 0	$ 0	$ 0