Stockholders' Equity (Tables)

6 Months Ended

Jun. 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		Six Months Ended
	June 30,		June 30,
	2018	2017	2018	2017
Dividend yield	0.0%	0.0%	0.0%	0.0%
Risk-free interest rate	2.6% - 2.8%	1.7% - 1.9%	2.5% - 2.8%	1.7% - 1.9%
Expected life (in years)	5	5	5	5
Historical volatility	43.7% - 48.4%	46.6% - 47.6%	43.7% - 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	1,765		14.10
Exercised	(2,273	)	10.73
Cancelled or expired	(274	)	9.49
Balance outstanding at June 30, 2018	7,177		$	11.58	7.03	$	68,433
Options vested and expected to vest	6,189		$	11.46	6.66	$	59,773
Options exercisable at June 30, 2018	3,658		$	11.04	4.99	$	36,802

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 June 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 - $7.45	708	5.26	$	6.33	485	$	6.01
$7.60 - $7.60	748	8.39	7.60		214	7.60
$7.95 - $9.55	830	6.59	9.20		583	9.21
$9.90 - $10.13	727	6.03	10.09		650	10.09
$10.31 - $11.95	726	7.50	11.23		377	10.84
$11.96 - $12.32	87	3.04	12.12		88	12.12
$12.45 - $12.45	930	9.63	12.45		—	—
$12.46 - $13.59	810	4.07	13.28		747	13.26
$14.30- $15.85	726	9.33	14.60		16	15.77
$15.96 - $21.75	885	6.60	17.87		498	17.27
	7,177	7.03	$	11.58	3,658	$	11.04

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	1,843		15.13		—
Released	(251	)	9.05		—
Forfeited	(107	)	8.02		—
Non-vested and outstanding at June 30, 2018	2,608		$	13.38	$	55,026
Expected to vest	1,798		$	12.80	$	37,936