Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 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
	March 31,
	2018	2017
Dividend yield	0.0%	0.0%
Risk-free interest rate	2.5% - 2.7%	1.9%
Expected life (in years)	5	5
Historical volatility	47.9% - 48.2%	47.0%

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	1,378		12.82
Exercised	(735	)	8.95
Cancelled or expired	(174	)	9.22
Balance outstanding at March 31, 2018	8,428		$	11.24	6.46	$	43,795
Options vested and expected to vest	7,355		$	11.22	6.04	$	38,459
Options exercisable at March 31, 2018	4,661		$	11.43	4.33	$	23,614

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 March 31, 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 - $7.33	854	4.71	$	6.17	616	$	5.85
$7.45 - $7.60	872	8.32	7.59		115	7.55
$7.95 - $9.55	1,058	6.16	9.20		740	9.18
$9.90 - $10.13	1,013	5.43	10.09		802	10.09
$10.31 - $11.95	855	7.33	11.22		323	11.03
$11.96 - $12.32	111	3.31	12.16		111	12.16
$12.45 - $12.45	930	9.88	12.45		—	—
$12.46 - $13.37	984	4.12	13.19		976	13.19
$13.59- $15.55	914	8.89	14.28		170	13.59
$15.66 - $18.24	837	3.80	17.09		807	17.13
	8,427	6.46	$	11.24	4,661	$	11.43

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	724		13.12		—
Released	(124	)	9.73		—
Forfeited	(76	)	7.77		—
Non-vested and outstanding at March 31, 2018	1,647		$	10.83	$	23,935
Expected to vest	1,298		$	10.86	$	21,219