Share Based Compensation (Tables)

6 Months Ended

Jun. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Expense Related to Share-Based Payments

The table below summarizes the expense recognized related to share-based payments recognized for the three and six month periods ended June 30 (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2015		2014		2015		2014
Stock options	$	4,484	$	2,889	$	8,842	$	6,300
Restricted stock		9,065		4,798		21,658		11,999
Stock-based compensation	$	13,549	$	7,687	$	30,500	$	18,299

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 June 30, 2015 (in thousands):

	Unrecognized Compensation Cost		Weighted Average Period of Expense Recognition (in Years)
Stock options	$	71,153		1.80
Restricted stock		19,811		1.29
Total	$	90,964

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 six month period ended June 30, 2015 (shares and aggregate intrinsic value in thousands):

	Shares			Weighted Average Exercise Price		Options Exercisable at End of Period		Weighted Average Exercise Price of Exercisable Options		Weighted Average Fair Value of Options Granted During the Period		Aggregate Intrinsic Value
Outstanding at December 31, 2014		5,131		$	58.71		2,370	$	21.75			$	461,770
Granted		271			155.95					$	38.07
Exercised		(209	)		33.90								25,541
Forfeited		(25	)		105.36
Outstanding at June 30, 2015		5,168		$	64.60		2,476	$	23.68			$	472,719
Expected to vest as of June 30, 2015		5,168		$	64.60

Schedule of Weighted-Average Assumptions

The fair value of stock option awards granted was estimated using the Black-Scholes option pricing model during the six months ended June 30, 2015 and 2014, with the following weighted-average assumptions for grants during the period.

	June 30
	2015			2014
Risk-free interest rate		1.28	%		0.90	%
Dividend yield		—			—
Expected volatility		28.47	%		34.92	%
Expected life (in years)		4.0			3.8

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 six months ended June 30, 2015 (shares in thousands):

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2014		716		$	121.38
Granted		89			155.65
Vested		(100	)		123.33
Cancelled		(5	)		35.78
Unvested at June 30, 2015		700		$	126.67