Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock-based compensation expense and tax benefits

The following table reflects activity related to our stock-based compensation arrangements (in millions):

	Year Ended December 31,
	2018		2017		2016
Stock-based compensation expense:
Restricted stock	$	63	$	58	$	52
Performance awards	22		19		15
Stock options and other awards	1		—		1
Total stock-based compensation expense	$	86	$	77	$	68
Tax benefit recognized on stock-based compensation expense	$	18	$	27	$	24
Tax benefit realized for tax deductions resulting from exercises and vestings	32		44		33
Effect of tax deductions in excess of recognized stock-based compensation expense	20		24		22

Summary of restricted stock awards

The fair value of each restricted stock per share is equal to the market price of our common stock. A summary of the status of our restricted stock awards is presented in the following table.

	Number of Shares		Weighted- Average Grant-Date Fair Value Per Share
Nonvested shares as of January 1, 2018	1,401,040		$	69.82
Granted	628,908		92.12
Vested	(843,709	)	71.26
Forfeited	(9,661	)	69.97
Nonvested shares as of December 31, 2018	1,176,578		80.70

The following table reflects activity related to our restricted stock:

	Year Ended December 31,
	2018		2017		2016
Weighted-average grant-date fair value per share of restricted stock granted	$	92.12	$	79.32	$	59.00
Fair value of restricted stock vested (in millions)	80		71		46