Finance Receivables, Credit Quality Information and Allowance for Loan Losses - Aging of receivables (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Past due finance receivables
Total delinquent	$ 9,401	$ 11,395
Total delinquent (as a percent)	12.90%	11.60%
Loans in non-accrual status	$ 1,614	$ 1,560
Gross receivables (as a percent)	2.20%	1.60%
Short-term consumer loans
Past due finance receivables
Loans in non-accrual status	$ 44,908	$ 61,973
Medium-term consumer loans
Past due finance receivables
Loans in non-accrual status	28,244	36,357
Consumer Borrower
Aging of receivables
Current finance receivables	$ 63,751	$ 86,935
Current finance receivables (as a percent)	87.10%	88.40%
Past due finance receivables
Loans in non-accrual status	$ 73,152	$ 98,330	$ 80,155
Gross receivables (as a percent)	100.00%	100.00%
Consumer Borrower | Past due finance receivables (1 - 30 days)
Past due finance receivables
Total delinquent	$ 6,418	$ 8,207
Total delinquent (as a percent)	8.80%	8.40%
Consumer Borrower | Past due finance receivables (31 - 60 days)
Past due finance receivables
Total delinquent	$ 2,451	$ 2,834
Total delinquent (as a percent)	3.40%	2.90%
Consumer Borrower | Past due finance receivables (61 - 90 days)
Past due finance receivables
Total delinquent	$ 532	$ 354
Total delinquent (as a percent)	0.70%	0.40%
Consumer Borrower | Short-term consumer loans
Past due finance receivables
Loans in non-accrual status	$ 44,908		51,283
Consumer Borrower | Short-term consumer loans | Past due finance receivables (1 - 30 days)
Past due finance receivables
Total delinquent	$ 2,299	$ 2,645
Total delinquent (as a percent)	3.20%	2.70%
Consumer Borrower | Secure Short Term Consumer Loans | Past due finance receivables (1 - 30 days)
Past due finance receivables
Total delinquent	$ 1,229	$ 1,513
Total delinquent (as a percent)	1.70%	1.50%
Consumer Borrower | Unsecure Short Term Consumer Loans | Past due finance receivables (1 - 30 days)
Past due finance receivables
Total delinquent	$ 1,070	$ 1,132
Total delinquent (as a percent)	1.50%	1.20%
Consumer Borrower | Medium-term consumer loans
Past due finance receivables
Loans in non-accrual status	$ 28,244		$ 28,872
Consumer Borrower | Medium-term consumer loans | Past due finance receivables (1 - 30 days)
Past due finance receivables
Total delinquent	$ 4,119	$ 5,562
Total delinquent (as a percent)	5.60%	5.70%
Consumer Borrower | Medium-term consumer loans | Past due finance receivables (31 - 60 days)
Past due finance receivables
Total delinquent	$ 2,451	$ 2,834
Total delinquent (as a percent)	3.40%	2.90%
Consumer Borrower | Medium-term consumer loans | Past due finance receivables (61 - 90 days)
Past due finance receivables
Total delinquent	$ 532	$ 354
Total delinquent (as a percent)	0.70%	0.30%
Consumer Borrower | Secure Medium Term Consumer Loans | Past due finance receivables (1 - 30 days)
Past due finance receivables
Total delinquent	$ 812	$ 1,321
Total delinquent (as a percent)	1.10%	1.30%
Consumer Borrower | Secure Medium Term Consumer Loans | Past due finance receivables (31 - 60 days)
Past due finance receivables
Total delinquent	$ 331	$ 461
Total delinquent (as a percent)	0.50%	0.50%
Consumer Borrower | Secure Medium Term Consumer Loans | Past due finance receivables (61 - 90 days)
Past due finance receivables
Total delinquent	$ 12	$ 10
Total delinquent (as a percent)	0.00%
Consumer Borrower | Unsecured Medium Term Consumer Loans | Past due finance receivables (1 - 30 days)
Past due finance receivables
Total delinquent	$ 3,307	$ 4,241
Total delinquent (as a percent)	4.50%	4.30%
Consumer Borrower | Unsecured Medium Term Consumer Loans | Past due finance receivables (31 - 60 days)
Past due finance receivables
Total delinquent	$ 2,120	$ 2,373
Total delinquent (as a percent)	2.90%	2.40%
Consumer Borrower | Unsecured Medium Term Consumer Loans | Past due finance receivables (61 - 90 days)
Past due finance receivables
Total delinquent	$ 520	$ 344
Total delinquent (as a percent)	0.70%	0.30%