Overview and Basis of Presentation - Schedule of Cumulative Effects of New Revenue Standard on Income Statement (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue		$ 129,791	$ 93,888	[1]
Operating expenses:
Sales and marketing	[2]	65,058	46,269	[1]
Operating loss		(33,615)	(25,261)	[1]
Net loss		$ (29,325)	$ (25,081)	[1],[3],[4]
Net loss per share, basic and diluted (usd per share)		$ (0.28)	$ (0.26)	[1]
As Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue			$ 93,007
Operating expenses:
Sales and marketing			47,301
Operating loss			(27,174)
Net loss			$ (26,994)
Net loss per share, basic and diluted (usd per share)			$ (0.28)
Adjustments | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue			$ 881
Operating expenses:
Sales and marketing			(1,032)
Operating loss			1,913
Net loss			$ 1,913
Net loss per share, basic and diluted (usd per share)			$ 0.02

[1] See Note 1 for a summary of adjustments.

[2] Includes share-based compensation expense as follows: Three Months EndedMarch 31,2018 2017 * As adjustedCost of revenue$3,098 $2,104Research and development10,231 6,914Sales and marketing8,007 5,524General and administrative5,652 4,562

[3] See Note 1 for a summary of adjustments.

[4] See Note 1 for a summary of adjustments.