Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock Option Activity

The following table summarizes stock option activity under our share-based plans for the year ended December 31, 2015:

	Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Balance at December 31, 2014	3,112,098	$	29.35
Granted	176,375	69.85
Less: Exercised	543,028	31.56
Forfeited	3,700	35.82
Balance at December 31, 2015	2,741,745	$	31.50	4.58	$	135,100,939
Exercisable at December 31, 2015	1,820,919	$	23.86	3.29	$	103,643,264

Stock options outstanding and exercisable by exercise price range

The following table presents information about stock options outstanding and exercisable at December 31, 2015:

	Outstanding Stock Options				Exercisable Stock Options
Range of Exercise Prices	Shares	Weighted Average Remaining Contractual Term (Years)	Weighted Average Exercise Price		Shares	Weighted Average Exercise Price
$ 18.00 to $ 20.34	1,223,199	3.17	$	19.66	1,223,199	$	19.66
$ 20.35 to $ 38.79	937,996	4.26	31.37		596,970	32.43
$ 38.80 to $ 69.85	580,550	8.06	56.67		750	57.91
	2,741,745	4.58	$	31.50	1,820,919	$	23.86

Summary of cash proceeds and tax benefits realized from stock option exercise.

The following table summarizes the cash proceeds and tax benefits realized from the exercise of stock options:

	Year Ended December 31,
(in thousands, except share amounts)	2015		2014		2013
Options exercised	543,028		441,833		780,485
Cash proceeds	$	17,137	$	12,451	$	20,323
Intrinsic value of options exercised	$	22,676	$	13,132	$	19,273
Tax benefits realized	$	8,326	$	5,018	$	7,364

Summary of assumptions for estimated fair value of employee stock option awards at grant date

We estimated the fair value of employee stock option awards at the grant date based on the assumptions summarized in the following table:

	Year Ended December 31,
(Weighted average)	2015				2014				2013
Expected volatility	33.8		%		37.7		%		38.7		%
Expected term	7.2			years	7.2			years	7.5			years
Risk-free interest rate	1.95		%		2.26		%		1.51		%
Expected dividend yield	1.5		%		1.5		%		1.5		%
Grant date fair value	$	22.57			$	21.07			$	16.42

Summary of restricted share actvity

The table below presents restricted stock awards activity under our share-based plans for the year ended December 31, 2015:

	Shares	Weighted Average Grant Date Fair Value
Balance unvested at December 31, 2014	365,859	$	37.47
Granted (at market price)	89,580	69.10
Less: Vested	147,619	27.89
Forfeited	6,060	55.56
Balance unvested at December 31, 2015	301,760	$	51.18

Total restricted stock awards that vested for the past three years and related fair value

The table below presents the total number of restricted stock awards that vested for the past three years and the related fair value of those awards (in thousands, except share amounts):

	2015		2014		2013
Shares vested	147,619		212,794		102,536
Fair value of restricted stock awards vested	$	10,182	$	12,354	$	4,544

Number of shares purchased by employees under the employee stock purchase plan

For the two six month offering periods in each year presented below, our employees purchased the following aggregate number of shares:

2015	2014	2013
22,555	22,508	26,644

Restricted [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of share-based compensation expense and recognized tax benefits [Table Text Block]

The following table presents the total share-based compensation expense for restricted stock awards for the past three years (in thousands):

	2015		2014		2013
Share-based compensation expense	$	5,513	$	5,203	$	4,103

Options [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of share-based compensation expense and recognized tax benefits [Table Text Block]

The following table presents the total share-based compensation expense for stock option awards and the related recognized tax benefits for the past three years (in thousands):

	2015		2014		2013
Share-based compensation expense	$	3,688	$	3,632	$	3,746
Recognized tax benefits	1,331		1,388		1,431