Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenues	$ 1,312,151	$ 1,007,257	$ 683,067
Costs and expenses:
Operations and support	675,471	454,321	269,453
Sales and marketing	310,299	214,290	150,730
Technology (exclusive of amortization)	115,297	82,278	56,263
General and administrative	101,918	85,465	65,023
Depreciation and amortization	115,449	85,940	51,848
Total costs and expenses	1,318,434	922,294	593,317
Income (loss) from operations	(6,283)	84,963	89,750
Interest expense - net	20,493	3,530	102
Income (loss) before provision for income taxes	(26,776)	81,433	89,648
Income tax (benefit) expense	(8,210)	2,952	(9,335)
Net income (loss) attributable to common stockholders	$ (18,566)	$ 78,481	$ 98,983
Net income (loss) per share attributable to common stockholders:
Basic	$ (0.20)	$ 0.88	$ 1.15
Diluted	$ (0.20)	$ 0.85	$ 1.12
Weighted-average shares used to compute net income (loss) per share attributable to common stockholders:
Basic	91,247	89,447	86,297
Diluted	91,247	92,354	88,182