STOCK-BASED COMPENSATION

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement, Noncash Expense [Abstract]

Presented below is a summary of the stock-based compensation cost and associated tax benefit included in the accompanying consolidated statements of operations:


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Stock-based compensation cost	$	41	$	35	$	86	$	72
Tax benefit	$	10	$	7	$	21	$	14

During the first six months of 2021, the Company granted 0.1 million employee stock options, which had a weighted average grant date fair value of $67.41 per share based on the Black-Scholes option-pricing model. The Company also granted 0.5 million shares of restricted stock in the first six months of 2021, which had a weighted average grant date fair value of $277.22 per share. Both the employee stock options and restricted stock generally vest ratably over four years. Additionally, the Company granted 0.1 million shares of performance-based awards whereby the number of shares that ultimately vest are based on the achievement of certain non-market-based performance metrics of the Company over three years. The weighted average grant date fair value of these awards was $268.85 per share.

The following weighted average assumptions were used in determining the fair value for options granted in 2021:


Expected dividend yield	0.89	%
Expected stock volatility	28	%
Risk-free interest rate	0.81 %
Expected holding period	5.6 years

Unrecognized stock-based compensation expense at June 30, 2021 was $11 million and $230 million for stock options and unvested restricted stock, respectively, which is expected to be recognized over a weighted average period of 2.5 years and 2.6 years, respectively. Additionally, there was $39 million of unrecognized stock-based compensation expense relating to the aforementioned non-market-based performance-based awards, which is expected to be recognized over a weighted average period of 2.1 years.

The following tables summarize information relating to stock option exercises and restricted stock vesting:


	Six Months Ended June 30,
	2021		2020
Exercise of stock options:
Proceeds from stock option exercises	$	16	$	23
Aggregate intrinsic value	$	35	$	74
Tax benefit realized upon exercise	$	8	$	18
Number of shares exercised	0.2		0.4
Vesting of restricted stock:
Fair value of shares vested	$	187	$	193
Tax benefit realized upon vesting	$	43	$	45
Number of shares vested	0.7		0.8
Vesting of performance-based restricted stock:
Fair value of shares vested	$	28	$	70
Tax benefit realized upon vesting	$	7	$	17
Number of shares vested	0.1		0.3