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Stockholders' Equity (Tables)
 12 Months Ended
Dec. 31, 2021
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
 Number of
Shares		Weighted- Average Exercise Price
(per Share)
Balances as of December 31, 20188,699,941 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, 20196,111,561 20,859,326 $124.28 
New Shares Authorized17,500,000 — — 
Granted(1,909,476)1,909,476 432.34 
Exercised(4,088,612)58.35 
Expired— (3,380)27.54 
Balances as of December 31, 202021,702,085 18,676,810 $170.23 
Granted(1,556,725)1,556,725 554.11 
Exercised— (2,632,324)65.97 
Expired— (5,360)34.63 
Balances as of December 31, 202120,145,360 17,595,851 $219.83 
Vested and exercisable at December 31, 2021
17,595,851 $219.83 
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,
 202120202019
Dividend yield— %— %— %
Expected volatility
34% - 41%
37% - 45%
37% - 41%
Risk-free interest rate
1.08% - 1.62%
0.67% - 1.71%
1.74% - 2.74%
Suboptimal exercise factor
3.81 - 3.98
3.34 - 3.67
3.07 - 3.23
Valuation data:
Weighted-average fair value (per share)$259.01 $217.42 $156.60 
Total stock-based compensation expense (in thousands)403,220 415,180 405,376 
Total income tax impact on provision (in thousands)89,642 91,718 90,856