Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Fair Value of Employee Stock Options Estimated Using Weighted Average Assumptions

The fair value of employee stock options was estimated using the weighted average assumptions below. Each of these inputs is subjective and its determination generally requires significant judgment.

	Year Ended December 31
	2017			2016			2015
Expected term (in years)		6.1			6.1			6.1
Expected volatility		51.9	%		60.0	%		60.0	%
Risk-free interest rate		2.07	%		1.42	%		1.76	%
Dividend yield		0.0	%		0.0	%		0.0	%

Summary of Total Stock-Based Compensation Expense for Options, RSUs and ESPP Included in Consolidated Statements of Operations and Comprehensive Loss

The following table summarizes the total stock-based compensation expense for options, RSUs and ESPP included in the consolidated statements of operations for all periods presented (in thousands):

	Year Ended December 31
	2017		2016		2015
Cost of revenue	$	163	$	17	$	17
Research and development		1,733		203		165
Selling, general and administrative		8,227		1,651		1,228
Total stock-based compensation expense	$	10,123	$	1,871	$	1,410