Accounting for Share-Based Compensation 2 (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2014
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 166
Weighted average period expected to be recognized (in years)	2 years 6 months 0 days
Stock Option Awards [Member]
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	9
Weighted average period expected to be recognized (in years)	2 years 2 months 12 days
Restricted Stock Units [Member]
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	28
Weighted average period expected to be recognized (in years)	2 years 4 months 24 days
Restricted Stock Awards [Member]
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	93
Weighted average period expected to be recognized (in years)	2 years 4 months 24 days
Performance Share Units [Member]
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 36
Weighted average period expected to be recognized (in years)	3 years 1 month 6 days