Quarterly Financial Results (Unaudited) - Schedule of Quarterly Financial Results (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 144,022	$ 131,826	$ 122,576	$ 114,556	$ 106,541	$ 97,726	$ 89,093	$ 82,252
Cost of revenue	27,364	25,765	24,851	22,377	21,056	19,010	18,591	17,072
Gross profit	116,658	106,061	97,725	92,179	85,485	78,716	70,502	65,180	$ 412,623	$ 299,883	$ 209,102
Net loss	$ (11,492)	$ (18,663)	$ (18,225)	$ (15,448)	$ (11,535)	$ (10,583)	$ (9,521)	$ (8,075)	$ (63,828)	$ (39,714)	$ (45,562)
Basic and diluted net loss per share	$ (0.29)	$ (0.48)	$ (0.48)	$ (0.41)	$ (0.31)	$ (0.29)	$ (0.26)	$ (0.22)	$ (1.66)	$ (1.08)	$ (1.29)

The aggregate cost of goods produced and sold and services rendered during the reporting period.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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