5. Share Based Compensation

The Company accounts for stock-based compensation pursuant to relevant authoritative guidance, which requires measurement of compensation cost for all stock awards at fair value on the date of grant and recognition of compensation, net of estimated forfeitures, over the requisite service period for awards expected to vest. The Company has Equity Compensation Plans (the Plans) pursuant to which the Company’s board of directors may grant stock options or restricted stock to employees. The Company is authorized to issue grants of restricted stock and stock options to purchase up to 26,963,150 shares for the years ended December 31, 2014, 2013 and 2012, respectively. On May 13, 2013, the Company’s stockholders authorized an increase of 6,500,000 shares of common stock available for grant pursuant to the 2010 Equity Compensation Plan. Giving effect to this increase, there were 5,180,697 additional shares remaining available for grant under the Plans at December 31, 2014.

The table below summarizes the expense related to share-based payments for the years ended December 31 (in thousands):


	2014		2013		2012
Stock options	$	13,267	$	11,677	$	10,341
Restricted stock		24,382		14,999		8,934

Stock-based compensation	$	37,649	$	26,676	$	19,275

The tax benefits recorded on stock based compensation were $13.0 million, $9.8 million and $6.8 million for the years ended December 31, 2014, 2013 and 2012, respectively.

The following table summarizes the Company’s total unrecognized compensation cost related to stock-based compensation as of December 31, 2014:


	Unrecognized Compensation Cost		Weighted Average Period of Expense Recognition (in Years)
Stock options	$	70,502		2.05
Restricted stock		37,692		1.56

Total	$	108,194

Stock Options

Stock options are granted with an exercise price estimated to be equal to the fair market value on the date of grant, as authorized by the Company’s board of directors. Options granted have vesting provisions ranging from one to six years. Stock option grants are generally subject to forfeiture if employment terminates prior to vesting. The Company issues new shares upon stock option exercises.

The following summarizes the changes in the number of shares of common stock under option for the following periods (shares and aggregate intrinsic value in thousands):


	Shares			Weighted Average Exercise Price		Options Exercisable at End of Year		Weighted Average Exercise Price of Exercisable Options		Weighted Average Fair Value of Options Granted During the Year		Aggregate Intrinsic Value
Outstanding at December 31, 2011		8,341		$	15.51		4,394	$	10.13			$	119,802
Granted		1,223			36.94					$	10.82
Exercised		(2,925	)		9.38								129,488
Forfeited		(74	)		20.43

Outstanding at December 31, 2012		6,565			22.17		2,666		14.71				206,636
Granted		307			80.77						23.00
Exercised		(1,425	)		21.13								136,807
Forfeited		(116	)		28.68

Outstanding at December 31, 2013		5,331			25.68		2,589		16.57				487,673
Granted		1,544			135.16					$	42.77
Exercised		(1,429	)		20.75								182,904
Forfeited		(315	)		41.72

Outstanding at December 31, 2014		5,131		$	58.71		2,370	$	21.75			$	461,770
Vested and expected to vest at December 31, 2014		5,131		$	58.71

The following table summarizes information about stock options outstanding at December 31, 2014 (shares in thousands):


Exercise Price	Options Outstanding		Weighted Average Remaining Vesting Life in Years		Options Exercisable
$5.20 – 6.548		9		—		9
10.00 – 14.00		803		—		803
18.00 – 23.00		1,515		0.56		996
27.83 – 34.72		190		0.83		86
35.04 – 40.65		974		1.49		447
47.63 – 58.02		24		1.91		—
74.99 – 111.09		325		2.70		29
115.45 – 149.68		1,291		3.17		—

		5,131				2,370

The aggregate intrinsic value of options exercisable at December 31, 2014 was $300.9 million. The weighted average remaining contractual term of options exercisable at December 31, 2014 was 5.7 years.

The fair value of stock option awards granted was estimated using the Black-Scholes option pricing model with the following weighted-average assumptions for the years ended December 31 as follows:


	2014			2013			2012
Risk-free interest rate		1.24	%		0.76	%		0.59	%
Dividend yield		—			—			—
Expected volatility		34.61	%		34.95	%		36.49	%
Expected life (in years)		3.90			4.00			4.00

The Company considered the retirement and forfeiture provisions of the options and utilized its historical experience to estimate the expected life of the options.

The Company utilizes the volatility of the share price of the Company’s common stock to estimate the volatility assumption for the Black-Scholes option pricing model.

The risk-free interest rate is based on the yield of a zero coupon U.S. Treasury security with a maturity equal to the expected life of the option from the date of the grant.

The weighted-average remaining contractual life for options outstanding was 6.9 and 6.7 years at December 31, 2014 and 2013, respectively.

Restricted Stock

Awards of restricted stock and restricted stock units are independent of stock option grants and are generally subject to forfeiture if employment terminates prior to vesting. The vesting of the shares is generally based on the passage of time, performance or market conditions, or a combination of these. Shares vesting based on the passage of time have vesting provisions ranging from one to four years. The fair value of restricted stock shares based on performance is based on the grant date fair value of the Company’s stock.

The fair value of restricted stock shares granted with performance based market conditions was estimated using the Monte Carlo option pricing model with the following assumptions during 2013. There were no restricted stock shares granted based with performance based market conditions in 2014 and 2012.


	2013
Risk-free interest rate		0.42	%
Dividend yield		—
Expected volatility		30.00	%
Expected life (in years)		1.75

The risk-free interest rate and volatility assumptions were calculated consistently with those applied in the Black-Scholes options pricing model utilized in determining the fair value of the stock option awards.

The following table summarizes the changes in the number of shares of restricted stock and restricted stock units for the following periods (shares in thousands):


	Shares			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2011		840			23.15
Granted		131			41.69
Cancelled		(25	)		33.49
Issued		(474	)		22.05

Outstanding at December 31, 2012		472			28.98
Granted		358			92.16
Cancelled		(31	)		35.42
Issued		(165	)		30.93

Outstanding at December 31, 2013		634			67.83
Granted		467			146.12
Cancelled		(76	)		31.48
Issued		(309	)		74.56

Outstanding at December 31, 2014		716		$	121.38