Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

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

Share-based Compensation, Activity [Table Text Block]

Stock-based compensation and the income tax benefit recognized during the three months ended March 31, 2018 and 2017 were as follows:

	Three Months Ended March 31
($ in millions)	2018		2017
			As Restated
Stock-based compensation		$9		$9
Income tax benefit recognized		$2		$3

Details of Grants of Stock-based Compensation

Grants of stock-based compensation during the three months ended March 31, 2018 and 2017 were as follows:

	Three Months Ended March 31
	2018			2017
Grant Details	Shares	Fair Value		Shares	Fair Value
Stock options	517,433		$25.38	637,607		$21.15
Restricted stock units	168,432		$110.28	182,070		$95.86
Contingent shares (a)	49,278		$116.32	58,557		$100.00

(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 three months ended March 31, 2018 was calculated with the following weighted average assumptions:

Weighted average exercise price		$116.32
Risk-free interest rate	2.9		%
Expected life of option in years	6.5
Expected dividend yield	1.7		%
Expected volatility	21.1		%