Stock-Based Incentive Compensation Plans (Compensation expense for all stock-based incentive compensation plans) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	$ 38	$ 40	$ 31
Recognized tax benefit	13	14	11
Stock options [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	9	9	8
Performance Shares [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	12	10	5
Stock appreciation rights [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	2	5	1
Restricted Stock Units And Non-Vested Stock [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Compensation expense	$ 15	$ 16	$ 17