Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2022

Share-based Payment Arrangement [Abstract]

Weighted Average Assumptions Used

The weighted average assumptions used in the model are as follows:

Expected volatility of stock price	91%
Risk-free interest rate	0.18%
Valuation period	3 years
Dividend yield	—%

Stock Based Compensation Activity

The activity related to RSUs consisted of (in thousands of shares):

			Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in millions)
Time-based RSUs
	Outstanding at January 1, 2022		671	$	39.39
		Granted (a)	67	194.74
		Vested (b)	(260)	34.00
		Forfeited	(6)	36.03
	Outstanding and expected to vest at March 31, 2022 (c)		472	$	64.49	1.1	$	124
Performance-based and market-based RSUs
	Outstanding at January 1, 2022		886	$	35.40
		Granted (a)	96	194.74
		Vested (b)	(163)	34.82
		Forfeited	(15)	32.42
	Outstanding at March 31, 2022		804	$	54.58	1.5	$	212
	Outstanding and expected to vest at March 31, 2022 (c)		796	$	53.17	1.5	$	210

__________

(a)Reflects the maximum number of stock units assuming achievement of all performance-, market- and time-vesting criteria and does not include those for non-employee directors. The weighted-average fair value of time-based RSUs and performance-based RSUs granted during the three months ended March 31, 2021 was $63.12 and $62.27, respectively.

(b)The total fair value of RSUs vested during the three months ended March 31, 2022 and 2021 was $15 million and $11 million, respectively.

(c)Aggregate unrecognized compensation expense related to time-based RSUs and performance-based and market-based RSUs amounted to $55 million and will be recognized over a weighted average vesting period of 1.4 years.