Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

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

Schedule of Share-based Compensation, Activity [Table Text Block]

Stock-based compensation and the income tax benefit recognized during the three and six months ended June 30, 2017 and 2016 were as follows:

	Three Months Ended June 30				Six Months Ended June 30
($ in millions)	2017		2016		2017		2016
Stock-based compensation	$	8	$	16	$	24	$	26
Income tax benefit recognized	$	2	$	5	$	8	$	9

Details of Grants of Stock-based Compensation

Grants of stock-based compensation during the three and six months ended June 30, 2017 and 2016 were as follows:

	Six Months Ended June 30
	2017			2016
Grant Details	Shares	Fair Value		Shares	Fair Value
Stock options	590,058	$	21.15	719,969	$	17.89
Restricted stock units	215,105	$	97.48	242,525	$	91.37
Contingent shares (a)	57,817	$	110.20	57,910	$	95.00

(a) The number of contingent shares represents the target value of the award.

Weighted Average Assumptions Used in Calculating the Fair Value of Stock Option

The fair value of the stock option grants issued during the six months ended June 30, 2017 was calculated with the following weighted average assumptions:

Weighted average exercise price	$	101.53
Risk-free interest rate	2.4		%
Expected life of option in years	6.5
Expected dividend yield	1.8		%
Expected volatility	22.0		%