Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Stockholders' Equity Note [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:

	Shares Available for Grant		Options Outstanding				Weighted- Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in Thousands)
			Number of Shares		Weighted- Average Exercise Price (per Share)
Balances as of December 31, 2012	28,343,259		32,010,664		$	10.19
Granted	(4,499,040	)	4,499,040		29.85
Exercised	—		(11,821,418	)	10.54
Balances as of December 31, 2013	23,844,219		24,688,286		$	13.61
Granted	(3,819,011	)	3,819,011		57.55
Exercised	—		(5,661,880	)	10.81
Balances as of December 31, 2014	20,025,208		22,845,417		$	21.65
Granted	(3,179,892	)	3,179,892		82.67
Exercised	—		(5,029,553	)	15.38
Balances as of December 31, 2015	16,845,316		20,995,756		$	32.39	6.26	$	1,723,505
Vested and exercisable at December 31, 2015			20,995,756		$	32.39	6.26	$	1,723,505

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

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

	Year Ended December 31,
	2015			2014			2013
Dividend yield	—		%	—		%	—		%
Expected volatility	36% - 53%			41% - 48%			51% - 54%
Risk-free interest rate	2.03% - 2.29%			2.39% - 2.83%			1.87% - 2.71%
Suboptimal exercise factor	2.47 - 2.48			2.66 - 5.44			2.33 - 3.92
Valuation data:
Weighted-average fair value (per share)	$	39.22		$	30.17		$	16.25
Total stock-based compensation expense (in thousands)	124,725			115,239			73,100
Total income tax impact on provision (in thousands)	47,125			43,999			28,096