Ownership, Nature of Business - Estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Financial assets:
Restricted cash	$ 4,170	$ 4,175	$ 4,220	$ 4,585
Level 1 | Carrying Amount
Financial assets:
Cash and cash equivalents	57,511	53,208
Restricted cash	4,170	4,175
Level 1 | Fair Value
Financial assets:
Cash and cash equivalents	57,511	53,208
Restricted cash	4,170	4,175
Level 3 | Carrying Amount
Financial assets:
Finance receivables	82,476	84,364
Level 3 | Fair Value
Financial assets:
Finance receivables	82,476	84,364
Senior PIK notes payable | Level 3 | Carrying Amount
Financial liabilities:
Financial liabilities debt instrument	74,529	60,796
Senior PIK notes payable | Level 3 | Fair Value
Financial liabilities:
Financial liabilities debt instrument	74,529	60,796
Secured notes payable | Level 2 | Carrying Amount
Financial liabilities:
Financial liabilities debt instrument	40,000	42,000
Secured notes payable | Level 2 | Fair Value
Financial liabilities:
Financial liabilities debt instrument	40,000	42,000
Subsidiary notes payable | Level 2 | Carrying Amount
Financial liabilities:
Financial liabilities debt instrument	74,761	71,838
Subsidiary notes payable | Level 2 | Fair Value
Financial liabilities:
Financial liabilities debt instrument	$ 74,761	$ 71,838