Accounting for Share-Based Compensation 2 (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Dec. 31, 2013
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 116
Weighted average period expected to be recognized	2 years 1 month 6 days
Stock Option Awards [Member]
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	9
Weighted average period expected to be recognized	2 years 2 months 12 days
Restricted Stock Units [Member]
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	20
Weighted average period expected to be recognized	2 years 0 months 0 days
Restricted Stock Awards [Member]
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	63
Weighted average period expected to be recognized	2 years 0 months 0 days
Performance Share Units [Member]
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 24
Weighted average period expected to be recognized	2 years 6 months 0 days