Stock-Based Compensation Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Stock-Based Compensation Expense and Related Tax Benefit [Table Text Block]

Stock-based compensation expense and the related tax benefit were as follows:



	Three Months Ended March 31,
	2016		2015
	(in thousands)
Stock options	$	554	$	649
Restricted stock units	3,096		3,326
Unrestricted stock awards	250		133
Phantom stock units	76		—
Total stock-based compensation	$	3,976	$	4,108

Related tax benefit	$	1,208	$	1,149

Stock Options, Valuation Assumptions [Table Text Block]

The fair values of stock options granted were estimated at the date of grant using the Black-Scholes option-pricing model with the following weighted average assumptions:



	Three Months Ended March 31,
	2016		2015
Dividend yield	—	%	—	%
Expected volatility	33.5	%	34.5	%
Risk-free interest rate	1.3	%	1.7	%
Expected term (years)	5.5		5.5

Employee Stock Options Activity [Table Text Block]

A summary of our stock option activity is as follows:



	Shares		Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value⁽¹⁾		Weighted Average Grant Date Fair Value
	(in thousands)				(years)	(in thousands)
Outstanding, January 1, 2015	1,123		$	51.90	4.4	$	1,676
Granted	204		35.29					$	12.15
Exercised	(2	)	26.65			17
Expired	(1	)	37.40
Outstanding, March 31, 2015	1,324		$	49.39	5.5	$	451

Outstanding, January 1, 2016	1,180		$	48.31
Granted	185		40.04					$	13.15
Exercised	(12	)	35.29			73
Forfeited	(35	)	35.29
Expired	(1	)	48.51
Outstanding, March 31, 2016	1,317		$	47.61	5.5	$	2,859

Exercisable March 31, 2016	892		$	52.46	3.6	$	1,040

Expected to vest, March 31, 2016	404		$	37.42	9.4	$	1,736

⁽¹⁾

The aggregate intrinsic value of outstanding stock options represents amounts that would have been received by the optionees had all in- the-money options been exercised on that date. Specifically, it is the amount by which the market value of our stock exceeded the exercise price of the outstanding in-the-money options before applicable income taxes, based on our closing stock price on the last business day of the period. The aggregate intrinsic value of stock options exercised during the period is calculated based on our stock price at the date of exercise.

Restricted Stock Units, Valuation Assumptions

The weighted-average assumptions used to estimate the fair value of performance-based restricted stock units granted and the resulting weighted average fair value are as follows:



	Three Months Ended March 31,
	2016			2015
Dividend yield	—		%	—		%
Expected volatility	30.0		%	30.1		%
Risk-free interest rate	0.7		%	0.7		%
Expected term (years)	1.8			2.1

Weighted average fair value	$	44.77		$	33.46

Restricted Stock Units Award Activity [Table Text Block]

The following table summarizes restricted stock unit activity:



	Number of Restricted Stock Units		Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value⁽¹⁾
	(in thousands)				(in thousands)
Outstanding, January 1, 2015	682
Granted⁽²⁾	315		$	35.30
Released	(266	)			$	10,888
Forfeited	(22	)
Outstanding, March 31, 2015	709

Outstanding, January 1, 2016	756
Granted⁽²⁾	172		$	40.02
Released	(262	)			$	10,098
Forfeited	(30	)
Outstanding, March 31, 2016	636

Vested but not released, March 31, 2016	5				$	207

Expected to vest, March 31, 2016	506				$	21,106


⁽¹⁾	The aggregate intrinsic value is the market value of the stock, before applicable income taxes, based on the closing price on the stock release dates or at the end of the period for restricted stock units expected to vest.


⁽²⁾	Restricted stock units granted in 2015 and 2016 do not include awards under the Performance Award Agreement for the respective years, as these awards are not granted until attainment of annual performance goals has been determined at the conclusion of the performance period, which had not occurred as of March 31, 2015 and 2016, respectively.

Schedule of Other Share-based Compensation, Activity [Table Text Block]

The following table summarizes phantom stock unit activity:



	Number of Phantom Stock Units	Weighted Average Fair Value
	(in thousands)
Outstanding, January 1, 2016	—
Granted	61	$	41.72
Outstanding, March 31, 2016	61	$	41.72

Expected to vest, March 31, 2016	53	$	41.72

Nonrestricted Stock Awards Activity [Table Text Block]

The following table summarizes unrestricted stock award activity:



	Three Months Ended March 31,
	2016		2015
	(in thousands, except per share data)
Shares of unrestricted stock granted	7		3

Weighted average grant date fair value per share	$	35.61	$	41.56

Employee Stock Purchase Plan (ESPP) Activity [Table Text Block]

The following table summarizes ESPP activity:



	Three Months Ended March 31,
	2016	2015
	(in thousands)
Shares of stock sold to employees⁽¹⁾	11	10


⁽¹⁾	Stock sold to employees during each fiscal quarter under the ESPP is associated with the offering period ending on the last day of the previous fiscal quarter.