STOCK-BASED COMPENSATION

3 Months Ended

Mar. 31, 2020

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 March 31,
	2020		2019
Stock-based compensation cost	$	37	$	36
Tax benefit	$	7	$	8

During the first three months of 2020, the Company granted 0.1 million employee stock options, which had a weighted average grant date fair value of $60.53 per share based on the Black-Scholes option-pricing model. The Company also granted 0.5 million shares of restricted stock in the first three months of 2020, which had a weighted average grant date fair value of $280.42 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 $273.85 per share.

The following weighted average assumptions were used in determining the fair value for options granted in 2020:


Expected dividend yield	0.80	%
Expected stock volatility	22.43	%
Risk-free interest rate	1.45	%
Expected holding period	5.7 years

Unrecognized stock-based compensation expense at March 31, 2020 was $10 million and $252 million for stock options and unvested restricted stock, respectively, which is expected to be recognized over a weighted average period of 2.6 years and 2.8 years, respectively. Additionally, there was $31 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 2.3 years.

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


	Three Months Ended March 31,
	2020		2019
Exercise of stock options:
Proceeds from stock option exercises	$	13	$	12
Aggregate intrinsic value	$	46	$	36
Tax benefit realized upon exercise	$	11	$	9
Number of shares exercised	0.2		0.3
Vesting of restricted stock:
Fair value of shares vested	$	191	$	147
Tax benefit realized upon vesting	$	44	$	34
Number of shares vested	0.8		0.8
Vesting of performance-based restricted stock:
Fair value of shares vested	$	70	$	48
Tax benefit realized upon vesting	$	17	$	12
Number of shares vested	0.3		0.3