Fair Value Measurements 3 (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Sep. 30, 2014	Mar. 31, 2014
Cash and Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Fair value disclosure	$ 1,040	$ 1,277
Other Noncurrent Assets, Net [Member] | Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other noncurrent assets, net, Fair value disclosure	less than $1 million	less than $1 million
Accrued Expenses and Other Current Liabilities [Member] | Facility Exit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Accrued expenses and other current liabilities, Fair value disclosure	9	11
Other Noncurrent Liabilities [Member] | Facility Exit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other noncurrent liabilities, Fair value disclosure	$ 14	$ 18