Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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,
	2015		2014		2013
Stock-based compensation expense:
Restricted stock	$	47	$	43	$	49
Performance awards	11		15		11
Stock options	1		2		4
Total stock-based compensation expense	$	59	$	60	$	64
Tax benefit recognized on stock-based compensation expense	$	21	$	21	$	22
Tax benefit realized for tax deductions resulting from exercises and vestings	66		64		66
Effect of tax deductions in excess of recognized stock-based compensation expense reported as a financing cash flow	44		47		47

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,
	2015		2014		2013
Weighted-average grant-date fair value per share of restricted stock granted	$	70.07	$	49.40	$	39.55
Fair value of restricted stock vested	69		60		74

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 table below.

	Number of Shares		Weighted- Average Grant-Date Fair Value Per Share
Nonvested shares as of January 1, 2015	1,758,150		$	41.96
Granted	829,213		70.07
Vested	(1,016,862	)	41.72
Forfeited	(19,061	)	41.42
Nonvested shares as of December 31, 2015	1,551,440		57.15

Summary of performance awards

A summary of the status of our performance awards is presented below.

	Nonvested Awards		Weighted- Average Grant-Date Fair Value Per Share
Awards outstanding as of January 1, 2015	614,390		$	42.06
Granted	183,299		88.97
Vested	(388,561	)	38.77
Forfeited	(703	)	48.57
Awards outstanding as of December 31, 2015	408,425		66.23

Performance awards converted during the year ended December 31, 2015 were as follows:

	Vested Awards Converted	Actual Conversion Rate	Number of Shares Issued
2011 awards	213,299	166.7%	355,576
2012 awards	96,845	200.0%	193,690
2013 awards	78,417	200.0%	156,834
Total	388,561		706,100