STOCK BASED COMPENSATION

At June 30, 2015, we had the following stock option and stock purchase plans:


•	the 2014 Incentive Stock Plan, which our stockholders approved in May 2014;


•	the 2011 Incentive Stock Plan, which our stockholders approved in May 2011;


•	the 2008 Incentive Stock Plan, which our stockholders approved in May 2008;


•	the 2005 Incentive Stock Plan, which our stockholders approved in April 2005;


•	the 2000 Nonstatutory Stock Option Plan, which expired in February 2010;


•	the 1997 Stock Option Plan, which expired in January 2007;


•	the 1996 Directors Stock Option Plan, which expired in May 2006; and


•	the Employee Stock Purchase Plan ("ESPP"), which our stockholders approved in May 2001.

Stock-Based Compensation Expense:

The following table presents the total stock-based compensation expense resulting from stock option awards, restricted stock units ("RSUs"), and the ESPP included in the Condensed Consolidated Statements of Income:



In thousands
	Three Months Ended June 30,				Six Months Ended June 30,
	2015		2014		2015		2014
Cost of revenues – stock option plan	$	22	$	21	$	45	$	28
Selling, general and administrative – stock option plan	4,650		3,818		9,379		7,859
Selling, general and administrative – RSUs	375		314		721		629
Selling, general and administrative – ESPP	370		299		759		608
Total pre-tax expense	$	5,417	$	4,452	$	10,904	$	9,124

The following table sets forth the tax benefits related to stock compensation:



In thousands
	Three Months Ended June 30,				Six Months Ended June 30,
	2015		2014		2015		2014
Tax benefit recognized in Statement of Income	$	1,134	$	1,020	$	3,602	$	1,929
Excess tax benefit of stock options exercised	2,677		3,346		10,899		7,080

Stock Options:

Stock option activity for the six months ended June 30, 2015, is summarized as follows:



	Number of Options		Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life	Total Aggregate Intrinsic Value
					(in years)	(in thousands)
Outstanding at beginning of year	5,377,857		$	80.88
Granted	935,276		130.97
Exercised	(583,441	)	67.31
Forfeited	(99,046	)	107.59
Canceled or expired	(1,228	)	107.03
Outstanding at June 30, 2015	5,629,418		$	90.15	6.07	$	246,741
Exercisable at June 30, 2015	3,035,083		$	72.39	5.17	$	186,748
Vested and expected to vest at June 30, 2015	5,374,237		$	88.93

As of June 30, 2015, there was $43.5 million of total unrecognized compensation expense related to non-vested option awards, which is expected to be recognized over a weighted average period of 3.26 years.

The following table sets forth the total intrinsic value of options exercised:



In thousands
	Three Months Ended June 30,				Six Months Ended June 30,
	2015		2014		2015		2014
Total intrinsic value of options exercised	$	10,125	$	14,721	$	39,650	$	26,517

The total intrinsic value of options exercised represents the total pre-tax value (the difference between the sales price on that trading day the option was exercised and the exercise price associated with the respective option).

The Company uses historical data to estimate expected life and volatility. The estimated fair value of stock options at the time of the grant using the Black-Scholes option pricing model was as follows:



	Three Months Ended June 30,						Six Months Ended June 30,
	2015			2014			2015			2014
Stock options granted (shares)	74,742			108,705			935,276			963,483
Weighted average fair value at grant date (per share)	$	22.18		$	21.40		$	22.80		$	21.30
Assumptions:
Expected term (in years)	4.79			4.69			4.79			4.74
Expected volatility	15.98		%	17.52		%	16.58		%	17.60		%
Expected dividend yield	—		%	—		%	—		%	—		%
Risk free interest rate	1.43		%	1.53		%	1.44		%	1.49		%

Restricted Stock Units:

Restricted stock units ("RSUs") vest at the end of three or five years. Our 2008, 2011 and 2014 Plans include a share reserve related to RSUs granted at a 2-1 ratio. A summary of the status of our non-vested RSUs and changes during the six months ended June 30, 2015, are as follows:



	Number of Units		Weighted Average Grant Date Fair Value		Total Aggregate Intrinsic Value
					(in thousands)
Non-vested at beginning of year	63,600		$	96.04
Granted	10,124		130.19
Vested and released	—		—
Forfeited	(3,537	)	101.56
Non-vested at June 30, 2015	70,187		$	100.69	$	9,399

As of June 30, 2015, there was $4.6 million of total unrecognized compensation expense related to RSUs, which is expected to be recognized over a weighted average period of 2.67 years.