Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Weighted Average Assumptions of Fair Value Options Using Black-Scholes Option-Pricing Model

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions:

	Three Months Ended		Nine Months Ended
	September 30,		September 30,
	2018	2017	2018	2017
Dividend yield	0.0%	0.0%	0.0%	0.0%
Risk-free interest rate	2.8% - 2.9%	1.8%	2.5% - 2.9%	1.7% - 1.9%
Expected life (in years)	5	5	5	5
Historical volatility	43.5% - 43.7%	47.3%	43.5% - 48.4%	46.6% - 47.6%

Summary of Stock Option Activity and Weighted Average Exercise Prices

A summary of the Company’s stock option activity and weighted average exercise prices follows:

	Stock Option Activity				Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
	Options (in thousands)		Weighted Average Exercise Price
Balance outstanding at December 31, 2017	7,959		$	10.71
Granted	1,952		15.03
Exercised	(2,874	)	10.72
Cancelled or expired	(554	)	9.91
Balance outstanding at September 30, 2018	6,483		$	12.07	6.91	$	90,038
Options vested and expected to vest	5,614		$	11.80	6.55	$	79,474
Options exercisable at September 30, 2018	3,250		$	11.00	4.78	$	48,604

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range

The following table summarizes information about outstanding and vested stock options as of September 30, 2018:

	Options Outstanding				Options Exercisable
Range of Exercise Prices	Number of Shares Outstanding (in thousands)	Weighted-Average Remaining Contractual Life (Years)	Weighted-Average Exercise Price		Number of Shares (in thousands)	Weighted-Average Exercise Price
$1.79 - $7.60	1,152	6.47	$	6.92	583	$	6.43
$7.95 - $9.55	664	6.35	9.21		479	9.21
$9.90 - $10.13	659	5.72	10.09		655	10.09
$10.31 - $11.96	674	7.06	11.27		395	11.01
$12.09 - $12.32	41	2.85	12.29		41	12.29
$12.45 - $12.45	930	9.38	12.45		—	—
$12.46 - $13.59	759	3.76	13.28		702	13.26
$14.30- $15.96	697	8.72	14.72		61	15.94
$16.05 - $21.75	721	6.92	18.09		334	17.44
$22.35 - $27.25	186	9.82	23.84		—	—
	6,483	6.91	$	12.07	3,250	$	11.00

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

A summary of the Company’s restricted stock units (“RSUs”) activity and weighted average exercise prices follows:

	Restricted Stock Unit Activity
	Number of Shares (in thousands)		Weighted Average Grant Date Fair Value (Per Share)		Aggregate Fair Value (in thousands)
Balance outstanding at December 31, 2017	1,123		$	9.03	$	—
Awarded	2,130		16.35		—
Released	(334	)	9.04		—
Forfeited	(234	)	10.42		—
Non-vested and outstanding at September 30, 2018	2,685		$	14.71	$	69,673
Expected to vest	1,878		$	13.93	$	48,741