Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Stock-Based Compensation

Summary of stock options outstanding, vested and exercisable

				Weighted
		Weighted		average
		average		remaining	Aggregate
	Outstanding	exercise price		contractual life	Intrinsic Value
	Options	per share		(Years)	(in thousands)
Outstanding at December 31, 2016	5,997,372	$	10.18	7.30	$	145,270
Granted	577,690		34.77
Forfeited	(191,890)		18.75
Exercised	(1,562,590)		7.34
Expired	(2,893)		13.79
Outstanding at September 30, 2017	4,817,689	$	13.70	6.93	$	107,478
Vested and exercisable at September 30, 2017	3,313,087	$	10.34	6.28	$	84,939

Summary of restricted stock units activity

		Weighted
		average
		grant date fair value
	Number of Awards	per share
Outstanding at December 31, 2016	67,295	$	25.88
Granted	275,726		34.98
Forfeited	(32,796)		31.03
Vested and converted to shares	(38,302)		29.88
Outstanding at September 30, 2017	271,923	$	33.93
Expected to vest at September 30, 2017	271,923	$	33.93

Schedule of weighted average assumptions to estimate the fair value of stock options granted

	Nine Months Ended September 30,
	2017			2016
Expected term (years)		6.25			6.25
Expected volatility		40.00	%		50.00	%
Expected dividend yield		0.00	%		0.00	%
Weighted average risk-free interest rate		1.92	%		1.34	%
Weighted average grant date fair value	$	14.60		$	9.39