Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 43,799	$ 29,121	$ 9,611
Cost of revenue	3,448	2,211	945
Gross profit	40,351	26,910	8,666
Operating expenses:
Technology and development	8,586	6,961	4,762
Sales and marketing	28,073	22,297	13,841
General and administrative	20,197	16,069	16,883
Depreciation and amortization	4,586	3,754	2,176
Mark-to-market	148	1,263	0
Total operating expenses	61,590	50,344	37,662
Loss from continuing operations	(21,239)	(23,434)	(28,996)
Interest and other income (expense), net:
Interest expense	(268)	(129)	(10)
Other income (expense), net	1,460	(123)	30
Total interest and other income (expense), net	1,192	(252)	20
Loss from continuing operations before income taxes	(20,047)	(23,686)	(28,976)
(Benefit) provision for income taxes	(347)	164	200
Loss from continuing operations, net of income taxes	(19,700)	(23,850)	(29,176)
Gain on sale of discontinued operations, net of income taxes	14,626	0	0
Income (loss) from discontinued operations, net of income taxes	7,301	2,903	(14,054)
Total income (loss) from discontinued operations, net of income taxes	21,927	2,903	(14,054)
Net income (loss)	$ 2,227	$ (20,947)	$ (43,230)
Net income (loss) per share - basic and diluted
Loss from continuing operations, net of income taxes (usd per share)	$ (0.39)	$ (0.46)	$ (0.57)
Income (loss) from discontinued operations, net of income taxes (usd per share)	0.43	0.06	(0.27)
Net income (loss) (usd per share)	$ 0.04	$ (0.40)	$ (0.84)
Weighted-average number of shares of common stock outstanding:
Basic and diluted weighted-average number of shares outstanding (shares)	50,511,366	52,279,738	51,684,397