Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2015

Stockholders' Equity and Stock-based Compensation Disclosure [Abstract]

Summary of Activity Related to Stock Option Plans

A summary of the activities related to the Company’s stock option plans, as adjusted for the Stock Split, is as follows:

			Options Outstanding
	Shares Available for Grant		Number of Shares		Weighted- Average Exercise Price (per share)		Weighted-Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in Thousands)
Balances as of December 31, 2014	20,025,208		22,845,417		$	21.65
Granted	(2,565,445	)	2,565,445		75.55
Exercised			(4,477,401	)	15.45
Balances as of September 30, 2015	17,459,763		20,933,461		$	29.58	6.32	$	1,544,838
Vested and exercisable as of September 30, 2015			20,933,461		$	29.58	6.32	$	1,544,838

Summary of Amounts Related to Option Exercises

A summary of the amounts related to option exercises, is as follows:

	Three Months Ended				Nine Months Ended
	September 30, 2015		September 30, 2014		September 30, 2015		September 30, 2014
	(in thousands)
Total intrinsic value of options exercised	$	118,259	$	60,337	$	313,880	$	208,057
Cash received from options exercised	$	35,089	$	9,877	$	69,809	$	56,794

Summary of Assumptions Used to Value Stock Option Grants Using Lattice-Binomial Model

The following table summarizes the assumptions used to value stock option grants using the lattice-binomial model and the valuation data, as adjusted for the Stock Split:

	Three Months Ended						Nine Months Ended
	September 30, 2015			September 30, 2014			September 30, 2015			September 30, 2014
Dividend yield	—		%	—		%	—		%	—		%
Expected volatility	45		%	43		%	36% - 45%			43% - 48%
Risk-free interest rate	2.29		%	2.52		%	2.03% - 2.29%			2.52% - 2.83%
Suboptimal exercise factor	2.48			2.68 - 4.57			2.47 -2.48			2.66 - 4.57
Valuation data:
Weighted-average fair value (per share)	$	50.58		$	33.85		$	34.64		$	31.03
Total stock-based compensation expense (in thousands)	$	32,834		$	29,878		$	88,865		$	84,988
Total income tax benefit related to stock options (in thousands)	$	12,365		$	11,438		$	33,553		$	32,562