Financing Receivables - Changes (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($) loan	Mar. 31, 2021 USD ($) loan
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 386
Provision for credit losses	638	$ 736
Ending Balance	578
Financing Receivable [Roll Forward]
Beginning Balance	71,152
Provision for credit losses	(638)	(736)
Ending Balance	$ 90,211
Participation interest in loan pool	5.00%
Advances
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 238	121
Provision for credit losses	267	(20)
Realized losses	0	0
Ending Balance	505	101
Financing Receivable [Roll Forward]
Beginning Balance	66,839
Provision for credit losses	(267)	20
Ending Balance	86,085
Loans and Loan Participations
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	148	125
Provision for credit losses	371	756
Realized losses	(446)	(767)
Ending Balance	73	114
Financing Receivable [Roll Forward]
Beginning Balance	4,313	5,333
Purchases, net	448	842
Proceeds from principal repayments, net	(307)	(419)
Accretion of loan discount	43	65
Provision for credit losses	(371)	(756)
Ending Balance	$ 4,126	5,065
Residential solar loans
Financing Receivable [Roll Forward]
Purchases, net		$ 100
Participation interest in loan pool	5.00%	5.00%
Number of loans purchased | loan		54
Indirect Channel Loans
Financing Receivable [Roll Forward]
Purchases, net	$ 500	$ 800
Number of loans purchased | loan	24	34