Financing Receivables - Aging of Loans and Loan Participations (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022 USD ($) loan	Dec. 31, 2021 USD ($) loan
Financing Receivable, Past Due [Line Items]
UPB	$ 91,158	$ 71,952
Loans in nonaccrual status	$ 0	$ 0
Loans and Loan Participations
Financing Receivable, Past Due [Line Items]
Loans | loan	3,745	3,901
UPB	$ 4,568	$ 4,875
Loans and Loan Participations | Customer Concentration Risk | Financing Receivable
Financing Receivable, Past Due [Line Items]
% of UPB	100.00%	100.00%
Loans and Loan Participations | Current
Financing Receivable, Past Due [Line Items]
Loans | loan	3,638	3,794
UPB	$ 4,425	$ 4,710
Loans and Loan Participations | Current | Customer Concentration Risk | Financing Receivable
Financing Receivable, Past Due [Line Items]
% of UPB	96.90%	96.60%
Loans and Loan Participations | Less than 30 days
Financing Receivable, Past Due [Line Items]
Loans | loan	82	74
UPB	$ 109	$ 107
Loans and Loan Participations | Less than 30 days | Customer Concentration Risk | Financing Receivable
Financing Receivable, Past Due [Line Items]
% of UPB	2.40%	2.20%
Loans and Loan Participations | 30 days
Financing Receivable, Past Due [Line Items]
Loans | loan	14	15
UPB	$ 16	$ 23
Loans and Loan Participations | 30 days | Customer Concentration Risk | Financing Receivable
Financing Receivable, Past Due [Line Items]
% of UPB	0.40%	0.50%
Loans and Loan Participations | 60 days
Financing Receivable, Past Due [Line Items]
Loans | loan	4	10
UPB	$ 4	$ 14
Loans and Loan Participations | 60 days | Customer Concentration Risk | Financing Receivable
Financing Receivable, Past Due [Line Items]
% of UPB	0.10%	0.30%
Loans and Loan Participations | 90+ days
Financing Receivable, Past Due [Line Items]
Loans | loan	7	8
UPB	$ 14	$ 21
Loans and Loan Participations | 90+ days | Customer Concentration Risk | Financing Receivable
Financing Receivable, Past Due [Line Items]
% of UPB	0.20%	0.40%
Loan Participations
Financing Receivable, Past Due [Line Items]
Loans | loan	3,729	3,885
UPB	$ 4,280	$ 4,584
Loan Participations | Current
Financing Receivable, Past Due [Line Items]
Loans | loan	3,622	3,780
UPB	$ 4,137	$ 4,442
Loan Participations | Less than 30 days
Financing Receivable, Past Due [Line Items]
Loans | loan	82	73
UPB	$ 109	$ 96
Loan Participations | 30 days
Financing Receivable, Past Due [Line Items]
Loans | loan	14	15
UPB	$ 16	$ 23
Loan Participations | 60 days
Financing Receivable, Past Due [Line Items]
Loans | loan	4	10
UPB	$ 4	$ 14
Loan Participations | 90+ days
Financing Receivable, Past Due [Line Items]
Loans | loan	7	7
UPB	$ 14	$ 9
Bank Partner Loans
Financing Receivable, Past Due [Line Items]
Loans | loan	16	16
UPB	$ 288	$ 291
Bank Partner Loans | Current
Financing Receivable, Past Due [Line Items]
Loans | loan	16	14
UPB	$ 288	$ 268
Bank Partner Loans | Less than 30 days
Financing Receivable, Past Due [Line Items]
Loans | loan	0	1
UPB	$ 0	$ 11
Bank Partner Loans | 30 days
Financing Receivable, Past Due [Line Items]
Loans | loan	0	0
UPB	$ 0	$ 0
Bank Partner Loans | 60 days
Financing Receivable, Past Due [Line Items]
Loans | loan	0	0
UPB	$ 0	$ 0
Bank Partner Loans | 90+ days
Financing Receivable, Past Due [Line Items]
Loans | loan	0	1
UPB	$ 0	$ 12