Warrants (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Summary of Assumptions using Black- Scholes Option Pricing Model to estimate fair value

The Company used the Black-Scholes option-pricing model to estimate the fair value of the convertible preferred stock warrant upon conversion with the following assumptions:

	Upon the Closing of theMerger on July 23, 2015
Common Stock Warrants:
Expected term (in years)		5.0
Expected volatility (%)	31.8%
Risk-free interest rate (%)	1.7%
Expected dividend yield (%)	0%

The fair value of the placement warrants was measured at their grant dates using the Black-Scholes pricing model and the following weighted average assumptions:

	Upon Issuance
Common Stock Warrants:
Expected term (in years)		5.0
Expected volatility (%)	31.8%
Risk-free interest rate (%)	1.6%
Expected dividend yield (%)	0%

The fair value of the 2016 Placement Warrants of $9.9 million and $2.7 million at December 31, 2017 and 2016, respectively, was estimated using the Black-Scholes option pricing model and the following weighted-average assumptions:

	December 31,
	2017		2016
2016 Placement Warrants:
Expected term (in years)		5.7		6.7
Expected volatility (%)	62.1%		63.6%
Risk-free interest rate (%)	2.2%		2.3%
Expected dividend yield (%)	0%		0%

The fair value of the 2017 Placement Warrants of $12.5 million at December 31, 2017 was estimated using the Black-Scholes option pricing model and the following weighted-average assumptions:

	December 31, 2017
2017 Placement Warrants:
Expected term (in years)		6.1
Expected volatility (%)	62.3%
Risk-free interest rate (%)	2.3%
Expected dividend yield (%)	0%