Stock-Based Incentive Compensation Plans (Total unrecognized 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]
Unrecognized stock-based incentive compensation expense	$ 41	$ 39	$ 36
Stock options [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Unrecognized stock-based incentive compensation expense	8	9	6
Weighted average period (in years)	1 year 6 months	1 year 10 months 24 days	1 year 9 months 18 days
Performance Shares [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Unrecognized stock-based incentive compensation expense	9	9	9
Weighted average period (in years)	1 year 6 months	1 year 6 months	1 year 7 months 6 days
Stock appreciation rights [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Unrecognized stock-based incentive compensation expense	3	3	1
Weighted average period (in years)	3 years 2 months 12 days	3 years 4 months 24 days	3 years 3 months 18 days
Restricted Stock Units And Non-Vested Stock [Member]
Employee service share-based compensation, aggregate disclosures [Abstract]
Unrecognized stock-based incentive compensation expense	$ 21	$ 18	$ 20
Weighted average period (in years)	1 year	1 year 2 months 12 days	1 year 3 months 18 days