Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2019

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 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, 2016	13,289,953		22,437,347		$	44.83
Granted	(2,550,038	)	2,550,038		159.56
Exercised	—		(3,338,474	)	26.79
Expired	—		(1,561	)	3.25
Balances as of December 31, 2017	10,739,915		21,647,350		$	61.13
Granted	(2,039,974	)	2,039,974		311.66
Exercised	—		(3,205,911	)	38.66
Expired	—		(2,135	)	$	4.60
Balances as of December 31, 2018	8,699,941		20,479,278		$	89.61
Granted	(2,588,380	)	2,588,380		320.66
Exercised	—		(2,208,052	)	32.88
Expired	—		(280	)	6.74
Balances as of December 31, 2019	6,111,561		20,859,326		$	124.28	5.57	$	4,230,013
Vested and exercisable at December 31, 2019			20,859,326		$	124.28	5.57	$	4,230,013

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:

	Year Ended December 31,
	2019			2018			2017
Dividend yield	—		%	—		%	—		%
Expected volatility	37% - 41%			40% - 42%			34% - 37%
Risk-free interest rate	1.74% - 2.74%			2.61% - 3.09%			2.24% - 2.45%
Suboptimal exercise factor	3.07 - 3.23			2.80 - 3.01			2.48 - 2.63
Valuation data:
Weighted-average fair value (per share)	$	156.60		$	157.19		$	71.45
Total stock-based compensation expense (in thousands)	405,376			320,657			182,209
Total income tax impact on provision (in thousands)	90,856			67,575			61,842

Schedule of Changes in Accumulated Other Comprehensive Loss

The following table summarizes the changes in accumulated balances of other comprehensive loss, net of tax:

	Foreign currency
	(in thousands)
Balances as of December 31, 2017	$	(20,557	)
Other comprehensive income before reclassifications	975
Net decrease in accumulated other comprehensive loss	975
Balances as of December 31, 2018	$	(19,582	)
Other comprehensive loss before reclassifications	(3,939		)
Net increase in accumulated other comprehensive loss	(3,939		)
Balances as of December 31, 2019	$	(23,521	)