Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

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,
	2017		2016		2015
Stock-based compensation expense:
Restricted stock	$	58	$	52	$	47
Performance awards	19		15		11
Stock options	—		1		1
Total stock-based compensation expense	$	77	$	68	$	59
Tax benefit recognized on stock-based compensation expense	$	27	$	24	$	21
Tax benefit realized for tax deductions resulting from exercises and vestings	44		33		66
Effect of tax deductions in excess of recognized stock-based compensation expense (a)	24		22		44

_______________________________

(a) Effective January 1, 2016, the effect of tax deductions in excess of recognized stock-based compensation expense is reported as an operating cash flow. These amounts were previously reported as financing cash flows.

Summary of restricted stock awards

The following table reflects activity related to our restricted stock (in millions, except per share data):

	Year Ended December 31,
	2017		2016		2015
Weighted-average grant-date fair value per share of restricted stock granted	$	79.32	$	59.00	$	70.07
Fair value of restricted stock vested	71		46		69

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, 2017	1,566,950		$	60.68
Granted	739,393		79.32
Vested	(897,246	)	61.76
Forfeited	(8,057	)	61.22
Nonvested shares as of December 31, 2017	1,401,040		69.82