Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Revenues	$ 123,461	$ 85,662	$ 355,874	$ 261,866
Costs and expenses:
Sales and marketing	26,499	21,443	80,687	66,229
Operations and support	44,346	27,637	120,029	74,941
Technology (exclusive of amortization)	11,006	8,412	31,765	23,980
General and administrative	11,754	10,203	37,501	29,049
Depreciation and amortization	9,089	6,299	25,282	21,377
Total costs and expenses	102,694	73,994	295,264	215,576
Income before provision for income taxes	20,767	11,668	60,610	46,290
Provision for income taxes	7,585	4,801	24,690	19,501
Net income attributable to common stockholders	$ 13,182	$ 6,867	$ 35,920	$ 26,789
Net income per share attributable to common stockholders:
Basic	$ 0.15	$ 0.08	$ 0.42	$ 0.32
Diluted	$ 0.15	$ 0.08	$ 0.42	$ 0.31
Weighted-average shares used to compute net income per share attributable to common stockholders:
Basic	85,217	84,583	84,889	83,827
Diluted	86,424	85,867	85,957	85,599