Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Summary of Expense Related to Share-Based Payments

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

	2015		2014		2013
Stock options	$	44,260	$	13,267	$	11,677
Restricted stock		45,862		24,382		14,999
Stock-based compensation	$	90,122	$	37,649	$	26,676

Summary of Total Unrecognized Compensation Cost Related to Stock-Based Compensation

The following table summarizes the Company’s total unrecognized compensation cost related to stock-based compensation as of December 31, 2015 (cost in thousands):

	Unrecognized Compensation Cost		Weighted Average Period of Expense Recognition (in Years)
Stock options	$	44,643		0.89
Restricted stock		7,213		1.24
Total	$	51,856

Summary of Changes in Number of Shares of Common Stock Under Option

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, 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
Granted		654			154.56					$	35.32
Exercised		(586	)		33.97								63,863
Forfeited		(196	)		95.16
Outstanding at December 31, 2015		5,003		$	72.72		2,545	$	26.82			$	351,277
Expected to vest at December 31, 2015		5,003		$	72.72

Schedule of Weighted-Average Assumptions

The fair value of restricted stock shares granted based on market conditions was estimated using the Monte Carlo option pricing model with the following assumptions during 2013. There were no restricted stock shares granted with performance based conditions or market conditions in 2015 and 2014.

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

Summary of Changes in Number of Shares of Restricted Stock and Restricted Stock Units

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, 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
Granted		126			151.33
Cancelled		(52	)		135.92
Issued		(293	)		85.40
Outstanding at December 31, 2015		497		$	149.40

Stock Options [Member]

Schedule of Stock Options Exercise Price

The following table summarizes information about stock options outstanding at December 31, 2015 (shares in thousands):

Exercise Price	Options Outstanding		Weighted Average Remaining Vesting Life in Years		Options Exercisable
$10.00 – 27.83		1,938		0.07		1,713
29.99 – 40.65		995		0.50		712
47.63 – 58.02		5		1.07		—
74.99 – 111.09		231		1.72		55
115.45 – 138.47		347		2.52		63
146.36 – 158.24		1,487		2.44		2
		5,003				2,545

Schedule of Weighted-Average Assumptions

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

	2015			2014			2013
Risk-free interest rate		1.47	%		1.24	%		0.76	%
Dividend yield		—			—			—
Expected volatility		27.77	%		34.61	%		34.95	%
Expected life (in years)		4.46			3.90			4.00