Investments - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Gross unrealized gains	$ 215,000		$ 1,822,000
Gross unrealized loss	8,973,000		802,000
Carrying value	467,042,000		494,766,000
Interest receivable on securities	200,000		300,000
Investment in securities	0	$ 0
Securities past due	0		0
Impairment on beneficial interests	3,973,000	0
Reclassification to/(from) non-credit discount from/(to) the allowance for changes in payment expectations	311,000	(953,000)
Beneficial interests in securitization trusts
Debt Securities, Available-for-sale [Line Items]
Reversal of provision for credit losses	400,000	$ (15,000)
Beneficial interests in securitization trusts
Debt Securities, Available-for-sale [Line Items]
Gross unrealized gains	0		0
Gross unrealized loss	0		0
Carrying value	139,249,000		139,588,000
Investments in securities
Debt Securities, Available-for-sale [Line Items]
Carrying value	$ 327,800,000		$ 355,200,000