Stock-Based Compensation (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2015

Dec. 31, 2014

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,
	2014	2013
Shares available for granting under the 2002 Plan	31.4	30.3
Options outstanding	8.1	12.2
Total shares reserved for issuance ¹	39.5	42.5


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 for the periods ended June 30 is as follows:



(in millions)	Three Months				Six Months
	2015		2014		2015		2014
Stock option expense	$	3	$	6	$	9	$	9
Restricted stock and unit awards expense	16		24		28		38
Total stock-based compensation expense	$	19	$	30	$	37	$	47

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



(in millions)	Year Ended December 31,
	2014		2013		2012
Stock option expense	$	21	$	13	$	10
Restricted stock and unit awards expense	79		83		80
Total stock-based compensation expense	$	100	$	96	$	90

Tax benefit	$	38	$	37	$	35

Assumptions used in valuing the options granted

The following assumptions were used in valuing the options granted (in 2012, stock options were not granted as part of employees' total stock-based incentive awards):



	Year Ended December 31,
	2014		2013		2012
Risk-free average interest rate	0.1 - 2.9%		0.1 - 2.9%		N/A
Dividend yield	1.8 - 1.4%		2.09 - 2.07%		N/A
Volatility	18 - 41%		29 - 45%		N/A
Expected life (years)	6.25 - 6.21		6.1 - 6.2		N/A
Weighted-average grant-date fair value per option	$	23.41	$	14.46	N/A

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, 2013	12.2			$	41.78
Granted	0.8		¹	$	77.85
Exercised	(4.8	)		$	72.04
Canceled, forfeited and expired	(0.1	)		$	50.96
Options outstanding as of December 31, 2014	8.1			$	45.18	4.8	$	356
Options exercisable as of December 31, 2014	6.5			$	40.28	3.8	$	317



(in millions, except per award amounts)	Shares			Weighted-average grant-date fair value
Nonvested options outstanding as of December 31, 2013	1.3			$	14.46
Granted	0.8			$	23.41
Vested	(0.4		)	$	14.47
Forfeited	(0.1		)	$	15.68
Nonvested options outstanding as of December 31, 2014	1.6			$	19.00
Total unrecognized compensation expense related to nonvested options	$	12
Weighted-average years to be recognized over	2.1

Stock option exercised

Information regarding our stock option exercises is as follows:



(in millions)	Year Ended December 31,
	2014		2013		2012
Net cash proceeds from the exercise of stock options	$	193	$	258	$	299
Total intrinsic value of stock option exercises	$	168	$	158	$	120
Income tax benefit realized from stock option exercises	$	73	$	61	$	47

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, 2013	3.1			$	47.89
Granted	0.7			$	77.74
Vested	(1.9		)	$	44.54
Forfeited	(0.2		)	$	57.26
Nonvested shares as of December 31, 2014	1.7			$	61.56
Total unrecognized compensation expense related to nonvested awards	$	68
Weighted-average years to be recognized over	1.6



	Year Ended December 31,
	2014		2013		2012
Weighted-average grant-date fair value per award	$	77.74	$	44.22	$	44.38
Total fair value of restricted stock and unit awards vested	$	88	$	119	$	90
Tax benefit relating to restricted stock activity	$	30	$	33	$	32