Stock Compensation Plans and Other Compensation Arrangements (Unaudited) (Tables)

3 Months Ended

Mar. 31, 2018

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

Nonvested Restricted Stock Shares Activity [Table Text Block]

The following table presents the number of restricted stock rights (RSRs) and restricted performance stock rights (RPSRs) granted to employees under the company's long-term incentive stock plan and the grant date aggregate fair value of those stock awards for the periods presented:

	Three Months Ended March 31
in millions	2018		2017
RSRs granted	0.1		0.1
RPSRs granted	0.2		0.3
Grant date aggregate fair value	$	87	$	86

Cash Units and Cash Performance Units Aggregate Payout Amount [Table Text Block]

The following table presents the minimum and maximum aggregate payout amounts related to cash units (CUs) and cash performance units (CPUs) granted to employees in the periods presented:

	Three Months Ended March 31
$ in millions	2018		2017
Minimum aggregate payout amount	$	35	$	35
Maximum aggregate payout amount	196		198