Quarterly Results of Operations (Unaudited) - Summary (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018
Quarterly Financial Data [Abstract]
Total revenue	$ 16,397	$ 16,740	$ 19,404	$ 18,759	$ 19,855	$ 20,526	$ 21,338	$ 22,198
Interest expense	2,275	2,303	2,386	2,540	2,654	2,585	2,443	2,455	$ 9,504	$ 10,137
Provision for credit losses	11,165	7,871	8,374	5,426	8,563	8,989	10,146	9,752	32,836	37,450
Non-interest expense	8,934	7,847	7,966	8,801	8,165	8,138	8,185	8,679
Operating income (loss) before income taxes	(5,977)	(1,281)	678	1,992	473	814	564	1,312	(4,588)	3,163
Income tax expense (benefit)	(1,232)	(376)	96	572	(171)	3,712	220	500	(940)	4,261
Net income (loss)	$ (4,745)	$ (905)	$ 582	$ 1,420	$ 644	$ (2,898)	$ 344	$ 812	$ (3,648)	$ (1,098)
Earnings (loss) per share:
Basic (in dollars per share)	$ (0.60)	$ (0.12)	$ 0.07	$ 0.18	$ 0.08	$ (0.37)	$ 0.04	$ 0.10	$ (0.46)	$ (0.14)
Diluted (in dollars per share)	$ (0.60)	$ (0.12)	$ 0.07	$ 0.18	$ 0.08	$ (0.37)	$ 0.04	$ 0.10	$ (0.46)	$ (0.14)