Stock-based Compensation Expense (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Stock-Based Compensation Expense

The effect of stock-based compensation expense during the three years ended December 31, 2021 was as follows:

	2021		2020		2019
	(in millions)
Stock-based compensation expense by line item:
Cost of sales	$	6.3	$	5.6	$	5.6
Research and development expenses	268.3		262.7		224.6
Selling, general and administrative expenses	166.8		161.2		130.3
Total stock-based compensation expense included in costs and expenses	441.4		429.5		360.5
Income tax effect	(82.9)		(147.0)		(124.2)
Total stock-based compensation included in costs and expenses, net of tax	$	358.5	$	282.5	$	236.3

Schedule of Stock-Based Compensation Expense by Type of Award

The stock-based compensation expense by type of award during the three years ended December 31, 2021 was as follows:

	2021		2020		2019
	(in millions)
Stock-based compensation expense by type of award:
Restricted stock units (including PSUs)	$	384.3	$	360.4	$	254.3
Stock options	36.8		59.7		96.7
ESPP share issuances	24.4		13.0		11.2
Stock-based compensation expense related to inventories	(4.1)		(3.6)		(1.7)
Total stock-based compensation expense included in costs and expenses	$	441.4	$	429.5	$	360.5

Schedule of Unrecognized Stock-Based Compensation Expense

The following table sets forth our unrecognized stock-based compensation expense as of December 31, 2021, by type of award and the weighted-average period over which that expense is expected to be recognized:

	As of December 31, 2021
	Unrecognized Expense		Weighted-average Recognition Period
	(in millions)		(in years)
Type of award:
Restricted stock units (including PSUs)	$	423.3	1.91
Stock options	19.1		1.09
ESPP share issuances	12.6		0.54
Total unrecognized stock-based compensation expense	$	455.0

Schedule of Assumptions Used to Estimate the Grant Date Fair Value of Options

The fair value of each option granted during 2021, 2020 and 2019 was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:

	2021	2020	2019
Stock options granted	27,302	22,636	1,520,743
Expected stock price volatility	35.03%	35.87%	36.99%
Risk-free interest rate	0.86%	0.43%	2.32%
Expected term of options (in years)	4.50	4.67	4.27
Expected annual dividends	—	—	—

Schedule of Assumptions Used to Estimate the Grant Date Fair Value Employee Stock Purchase Plan

The following table reflects the weighted-average assumptions used in the Black-Scholes option pricing model for 2021, 2020 and 2019:

	2021	2020	2019
Expected stock price volatility	34.06%	37.70%	33.43%
Risk-free interest rate	0.05%	0.11%	2.08%
Expected term (in years)	0.69	0.71	0.74
Expected annual dividends	—	—	—