Quarterly Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly financial data
Revenue, net of refund liabilities	$ 49,633	$ 43,320	$ 42,102	$ 36,721	$ 47,074	$ 42,467	$ 38,510	$ 33,569	$ 171,776	$ 161,620	$ 140,844
Operating expenses:
Cost of revenue	26,493	26,146	27,389	24,797	26,746	26,675	25,605	23,026	104,825	102,052	91,299
Selling, general and administrative expenses	13,862	12,521	12,809	11,264	12,792	12,189	11,424	10,536	50,456	46,941	39,399
Depreciation of property, equipment and software assets	2,074	1,713	2,360	1,223	1,107	1,133	1,109	1,220	7,370	4,569	5,033
Amortization of intangible assets	871	872	864	788	1,468	722	722	722	3,395	3,634	1,832
Acquisition-related adjustments (income) loss	12	(1,640)	0	0	(2,283)	0	0	0	(1,628)	(2,283)	0
Total operating expenses	43,312	39,612	43,422	38,072	39,830	40,719	38,860	35,504	164,418	154,913	137,563
Operating income from continuing operations	6,321	3,708	(1,320)	(1,351)	7,244	1,748	(350)	(1,935)	7,358	6,707	3,281
Foreign currency transaction losses (gains) on short-term intercompany balances	272	70	880	(220)	(263)	(418)	(957)	(552)	1,002	(2,190)	84
Interest expense, net	363	416	486	398	1,312	142	48	37	1,663	1,539	(153)
Other loss (income)	5	(1)	5	12	17	17	5	(199)	21	(160)	(121)
Net income from continuing operations before income tax	5,681	3,223	(2,691)	(1,541)	6,178	2,007	554	(1,221)	4,672	7,518	3,471
Income tax expense (benefit)	(252)	597	189	787	526	930	879	627	1,321	2,962	1,242
Net income from continuing operations	$ 5,933	$ 2,626	$ (2,880)	$ (2,328)	$ 5,652	$ 1,077	$ (325)	$ (1,848)	$ 4,593	$ 3,184	$ 905
Basic (loss) earnings per common share from continuing operations (usd per share)	$ 0.26	$ 0.11	$ (0.13)	$ (0.10)	$ 0.26	$ 0.05	$ (0.01)	$ (0.08)	$ 0.20	$ 0.15	$ 0.04
Diluted (loss) earnings per common share from continuing operations (usd per share)	$ 0.26	$ 0.11	$ (0.13)	$ (0.10)	$ 0.26	$ 0.05	$ (0.01)	$ (0.08)	$ 0.20	$ 0.15	$ 0.04