Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

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

Schedule of Stock-Based Compensation Expense

Stock-based compensation expense related to stock options, ESPP purchase rights, and RSUs during the three and nine months ended September 30, 2017 and 2016 is summarized as follows (in thousands):

	Three months ended September 30,						Nine months ended September 30,
	2017			2016			2017			2016
Stock-based compensation expense by type of award:
RSUs	$	3,545		$	7,979		$	18,875		$	24,931
ESPP purchase rights		1,103			574			3,666			1,932
Employee stock options		—			—			—			79
Total stock-based compensation		4,648			8,553			22,541			26,942
Income tax benefit		(1,525	)		(3,649	)		(6,929	)		(7,895	)
Stock-based compensation expense, net of tax	$	3,123		$	4,904		$	15,612		$	19,047

Schedule of ESPP Purchase Rights and Underlying Weighted Average Assumptions

Stock options were not granted during the three and nine months ended September 30, 2017 and 2016. The estimated weighted average fair value per share of ESPP purchase rights issued and the underlying weighted average assumptions for the three and nine months ended September 30, 2017 and 2016 are as follows:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2017			2016			2017			2016
Weighted average fair value per share	$	13.14		$	12.00		$	12.09		$	10.69
Expected volatility		25% - 28	%		26% - 32	%		24% - 28	%		22% - 32	%
Risk-free interest rate		1.2% - 1.3	%		0.4% - 0.7	%		0.7% - 1.3	%		0.4% - 0.8	%
Expected term (in years)		0.5 - 2.0			0.5 - 2.0			0.5 - 2.0			0.5 - 2.0

Schedule of Stock Options Outstanding and Exercisable

Stock options outstanding and exercisable, including performance-based and market-based options, as of September 30, 2017, and activity during the nine months ended September 30, 2017 are summarized below (in thousands, except weighted average exercise price and remaining contractual term):

	Shares outstanding			Weighted average exercise price		Weighted average remaining contractual term (years)		Aggregate intrinsic value
Options outstanding at January 1, 2017		315		$	13.86
Options exercised		(140	)		12.22
Options outstanding at September 30, 2017		175		$	15.18		1.32	$	4,812
Options vested and expected to vest at September 30, 2017		175		$	15.18		1.32	$	4,812
Options exercisable at September 30, 2017		175		$	15.18		1.32	$	4,812

Schedule of Non-Vested RSUs

Non-vested RSUs as of September 30, 2017, and activity during the nine months ended September 30, 2017 are summarized below (shares in thousands):

	Time-based					Performance-based					Market-based				Total
	Shares			Weighted average grant date fair value		Shares			Weighted average grant date fair value		Shares		Weighted average grant date fair value		Shares			Weighted average grant date fair value
Non-vested at January 1, 2017		795		$	43.79		1,265		$	42.64		23	$	33.16		2,083		$	43.34
Granted		120			45.98		371			46.93		—		—		491			46.70
Vested		(417	)		43.88		(276	)		40.83		—		—		(693	)		42.66
Forfeited		(49	)		43.72		(437	)		41.29		—		—		(486	)		41.53
Non-vested at September 30, 2017		449		$	44.30		923		$	45.55		23	$	33.16		1,395		$	45.49

Schedule of Weighted Average Grant Date Fair Value Per Share of Performance-Based RSUs and Market-based RSUs Assumptions Used to Estimate Fair Value

The weighted average grant date fair value per share of performance-based RSUs granted and the assumptions used to estimate grant date fair value during the nine months ended September 30, 2017 and 2016 are as follows:

	Performance-based
	RSUs
	Short-term		Long-term
Nine months ended September 30, 2017 Grants
Grant date fair value per share	$	47.23	$	45.96
Service period (years)		1.0		2.0 - 3.0
Nine months ended September 30, 2016 Grants
Grant date fair value per share	$	39.79	$	45.62
Service period (years)		1.0		2.0 - 3.0