Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2017

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 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, 2016	13,289,953		22,437,347		$	44.83
Granted	(719,874	)	719,874		136.82
Exercised	—		(939,217	)	26.69
Expired	—		(1,561	)	$	3.25
Balances as of March 31, 2017	12,570,079		22,216,443		$	48.58	6.1	$	2,204,541
Vested and exercisable as of March 31, 2017			22,216,443		$	48.58	6.1	$	2,204,541

Summary of Amounts Related to Option Exercises

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

	Three Months Ended
	March 31, 2017		March 31, 2016
	(in thousands)
Total intrinsic value of options exercised	$	107,097	$	31,457
Cash received from options exercised	$	24,178	$	3,536

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:

	Three Months Ended
	March 31, 2017			March 31, 2016
Dividend yield	—		%	—		%
Expected volatility	37		%	50		%
Risk-free interest rate	2.45		%	2.04		%
Suboptimal exercise factor	2.48			2.48
Weighted-average fair value (per share)	$	62.36		$	50.76
Total stock-based compensation expense (in thousands)	$	44,888		$	42,422
Total income tax impact on provision (in thousands)	$	14,701		$	15,963