Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

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

Number of Common Shares Reserved for Issuance

The number of common shares reserved for issuance are as follows:

(in millions)	December 31,
	2016	2015
Shares available for granting under the 2002 Plan	33.5	32.8
Options outstanding	3.8	5.8
Total shares reserved for issuance 1	37.3	38.6

¹ Shares reserved for issuance under the Director Deferred Stock Ownership Plan are not included in the total, but are approximately 0.1 million.

Stock-based Compensation Expense

Stock-based compensation expense and the corresponding tax benefit are as follows:

(in millions)	Year Ended December 31,
	2016		2015		2014
Stock option expense	$	7	$	14	$	21
Restricted stock and unit awards expense	69		64		79
Total stock-based compensation expense	$	76	$	78	$	100
Tax benefit	$	29	$	29	$	38

Assumptions Used in Valuing the Options Granted

The following assumptions were used in valuing the options granted:

	Year Ended December 31,
	2015		2014
Risk-free average interest rate	0.2 - 1.9%		0.1 - 2.9%
Dividend yield	1.4%		1.4 - 1.8%
Volatility	21 - 39%		18 - 41%
Expected life (years)	6.3		6.21 - 6.25
Weighted-average grant-date fair value per option	$	27.57	$	23.41

Stock Option Activity

Stock option activity is as follows:

(in millions, except per award amounts)	Shares		Weighted average exercise price		Weighted-average remaining years of contractual term	Aggregate intrinsic value
Options outstanding as of December 31, 2015	5.8		$	45.61
Exercised	(1.9	)	$	95.87
Canceled, forfeited and expired	(0.1	)	$	69.93
Options outstanding as of December 31, 2016	3.8		$	43.36	3.6	$	246
Options exercisable as of December 31, 2016	3.7		$	41.87	3.5	$	242

(in millions, except per award amounts)	Shares			Weighted-average grant-date fair value
Nonvested options outstanding as of December 31, 2015	0.8			$	19.82
Vested	(0.5		)	$	19.35
Forfeited	(0.1		)	$	21.84
Nonvested options outstanding as of December 31, 2016	0.2			$	23.42
Total unrecognized compensation expense related to nonvested options 1	$	—
Weighted-average years to be recognized over	0.3

¹  There is less than $1 million of unrecognized compensation expense related to nonvested options.

Stock Option Exercises

Information regarding our stock option exercises is as follows:

(in millions)	Year Ended December 31,
	2016		2015		2014
Net cash proceeds from the exercise of stock options	$	88	$	86	$	193
Total intrinsic value of stock option exercises	$	95	$	94	$	168
Income tax benefit realized from stock option exercises	$	41	$	49	$	73

Restricted Stock and Unit Activity

Restricted stock and unit activity for performance and non-performance awards is as follows:

(in millions, except per award amounts)	Shares			Weighted-average grant-date fair value
Nonvested shares as of December 31, 2015	1.2			$	92.39
Granted	0.9			$	93.01
Vested	(0.9		)	$	106.81
Forfeited	(0.2		)	$	95.41
Nonvested shares as of December 31, 2016	1.0			$	106.31
Total unrecognized compensation expense related to nonvested awards	$	55
Weighted-average years to be recognized over	1.7

	Year Ended December 31,
	2016		2015		2014
Weighted-average grant-date fair value per award	$	93.01	$	77.06	$	77.74
Total fair value of restricted stock and unit awards vested	$	99	$	155	$	88
Tax benefit relating to restricted stock activity	$	26	$	24	$	30