Stock Plans 2 (Details) $ in Millions	12 Months Ended
	Mar. 31, 2018 USD ($)
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 119
Weighted average period expected to be recognized (in years)	1 year 10 months 24 days
Stock Option Awards
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 4
Weighted average period expected to be recognized (in years)	1 year 9 months 18 days
Restricted Stock Units
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 18
Weighted average period expected to be recognized (in years)	1 year 9 months 18 days
Restricted Stock Awards
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 64
Weighted average period expected to be recognized (in years)	1 year 9 months 18 days
Performance Share Units
Unrecognized share-based compensation costs
Unrecognized share-based compensation costs	$ 33
Weighted average period expected to be recognized (in years)	2 years 2 months 12 days