Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Stock-Based Compensation Expense

This expense was allocated in the consolidated statements of comprehensive income as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Cost of revenues	$	494	$	319	$	1,414	$	916
Operating expenses
Sales and marketing		565		620		1,656		1,913
Research and development		241		143		698		422
General and administrative		1,047		930		3,065		2,753
Total stock-based compensation expense	$	2,347	$	2,012	$	6,833	$	6,004

Stock Option Activity

Our stock option activity was as follows:

				Weighted Average
	Options			Exercise Price
	(#)			($/share)
Outstanding at December 31, 2016		1,016,012		$	44.72
Granted		169,451			56.02
Exercised		(62,854	)		20.79
Forfeited		(10,622	)		56.12
Outstanding at September 30, 2017		1,111,987			47.69

Weighted Average Grant Date Fair Value of Options Granted, Assumptions

The weighted average grant date fair value of options granted during the first nine months of 2017 was $18.90 and this was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

Volatility	37.4	%
Dividend yield	0	%
Life (in years)	4.5
Risk-free interest rate	1.85	%

Fair Value Estimation of Common Stock Using Black-Scholes Option Pricing Model, Assumptions

The fair value was estimated based on the market price of our common stock at the beginning of the offering period using the Black-Scholes option pricing model with the following assumptions:

Volatility	26.0	%
Dividend yield	0	%
Life (in years)	0.5
Risk-free interest rate	0.62	%

Performance Share Units and Restricted Stock Units [Member]

Performance Share Units and Restricted Stock Units and Restricted Stock Awards

Activity for our performance share units and restricted stock units was as follows:

	Performance Share and			Weighted Average
	Restricted Stock Units			Grant Date Fair Value
	(#)			($/share)
Outstanding at December 31, 2016		189,042		$	54.14
Granted		207,738			55.74
Vested and common stock issued		(64,818	)		53.63
Forfeited		(4,805	)		54.55
Outstanding at September 30, 2017		327,157			55.25

Restricted Stock Award [Member]

Performance Share Units and Restricted Stock Units and Restricted Stock Awards

Our restricted stock awards activity was as follows:

	Restricted Stock			Weighted Average
	Awards			Grant Date Fair Value
	(#)			($/share)
Outstanding at December 31, 2016		1,524		$	52.28
Restricted common stock issued		5,454			58.29
Restrictions lapsed		(4,248	)		56.13
Forfeited		—			—
Outstanding at September 30, 2017		2,730			58.30