Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]

Estimated Weighted-average Fair Value per Share of Options Granted

The following assumptions were used to calculate our stock-based compensation for each stock option grant on the date of the grant:

	Year Ended
	December 31, 2017
Stock Options with only service conditions:
Expected volatility	39% - 42%
Expected term (in years)	4.89
Risk-free interest rate	1.78% - 2.47%
Dividend yield	—	%

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions

The following assumptions were used in the Black-Scholes options pricing model to calculate our stock-based compensation for each stock purchase right granted under the 2012 ESPP:

	Year Ended December 31,
	2019		2018		2017
ESPP:
Expected volatility	30% - 49%		26% - 31%		28% - 49%
Expected term (in years)	0.50		0.50		0.50
Risk-free interest rate	2.04% - 2.46%		1.15% - 2.22%		0.40% - 1.15%
Dividend yield	—	%	—	%	—	%