Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2020

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)
Balances as of December 31, 2019	6,111,561		20,859,326		$	124.28
New Shares Authorized	17,500,000		—		—
Granted	(1,095,065	)	1,095,065		375.86
Exercised	—		(2,208,741	)	60.06
Expired	—		(48	)	9.96
Balances as of June 30, 2020	22,516,496		19,745,602		$	145.42
Vested and exercisable as of June 30, 2020			19,745,602		$	145.42

Summary of Amounts Related to Option Exercises

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

	Three Months Ended				Six Months Ended
	June 30, 2020		June 30, 2019		June 30, 2020		June 30, 2019
	(in thousands)
Total intrinsic value of options exercised	$	442,156	$	212,932	$	745,382	$	393,774
Cash received from options exercised	89,060		21,896		132,754		44,868

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						Six Months Ended
	June 30, 2020			June 30, 2019			June 30, 2020			June 30, 2019
Dividend yield	—		%	—		%	—		%	—		%
Expected volatility	44		%	39		%	37% - 44%			39% - 41%
Risk-free interest rate	0.74		%	2.50		%	0.74% - 1.71%			2.50% - 2.74%
Suboptimal exercise factor	3.51			3.16			3.34 - 3.51			3.07 - 3.16
Weighted-average fair value (per share)	$	203		$	179		$	184		$	171
Total stock-based compensation expense (in thousands)	$	104,210		$	103,848		$	201,229		$	205,048
Total income tax impact on provision (in thousands)	$	22,834		$	24,845		$	44,143		$	46,473