CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 617,736	$ 384,402	$ 254,216
Costs and expenses:
Cost of revenue (exclusive of depreciation and amortization shown separately below)	17,223	13,764	9,370
Selling and marketing expense	432,784	261,100	172,849
General and administrative expense	71,541	37,227	30,030
Product development	17,925	13,761	10,485
Depreciation	7,085	4,944	3,008
Amortization of intangibles	12,992	1,243	149
Change in fair value of contingent consideration	23,931	0	0
Restructuring and severance	404	122	422
Litigation settlements and contingencies	718	129	(611)
Total costs and expenses	584,603	332,290	225,702
Operating income	33,133	52,112	28,514
Other (expense) income, net:
Interest expense, net	(7,028)	(561)	(171)
Other (expense) income	(396)	23	0
Income before income taxes	25,709	51,574	28,343
Income tax (expense) benefit	(6,291)	(20,366)	22,973
Net income from continuing operations	19,418	31,208	51,316
Loss from discontinued operations, net of tax	(3,840)	(3,714)	(3,269)
Net income	15,578	27,494	48,047
Comprehensive income	$ 15,578	$ 29,494	$ 48,047
Weighted average shares outstanding:
Weighted average basic common shares (in shares)	11,945	11,812	11,516
Weighted average diluted common shares (in shares)	13,682	12,773	12,541
Income per share from continuing operations:
Basic (in dollars per share)	$ 1.63	$ 2.64	$ 4.46
Diluted (in dollars per share)	1.42	2.44	4.09
Loss per share from discontinued operations:
Basic (in dollars per share)	(0.32)	(0.31)	(0.28)
Diluted (in dollars per share)	(0.28)	(0.29)	(0.26)
Net income per share:
Basic (in dollars per share)	1.30	2.33	4.17
Diluted (in dollars per share)	$ 1.14	$ 2.15	$ 3.83