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Debt and Financing Activities - Other Information (Details)	1 Months Ended		12 Months Ended
	May 26, 2017 EUR (€)	May 26, 2017 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)
Debt Instrument [Line Items]
Future principal payments of long-term debt in 2017			$ 1,057,000,000
Future principal payments of long-term debt in 2018			1,503,000,000
Future principal payments of long-term debt in 2019			11,000,000
Future principal payments of long-term debt in 2020			605,000,000
Future principal payments of long-term debt in 2021			641,000,000
Future principal payments of long-term debt, thereafter			4,545,000,000
Repayments of loan			1,601,000,000	$ 1,598,000,000	$ 353,000,000
Total debt outstanding			$ 8,362,000,000	8,107,000,000
Notes
Debt Instrument [Line Items]
Repayments of loan				93,000,000
0.95% Notes Due December 4 2015 \| Notes
Debt Instrument [Line Items]
Repayments of loan				$ 500,000,000
Debt interest rate (percent)				0.95%
3.25% Notes Due March 1 2016 \| Notes
Debt Instrument [Line Items]
Repayments of loan				$ 600,000,000
Debt interest rate (percent)				3.25%
Subsequent Event \| 4.50% Euro Bonds due April 26, 2017 \| Notes
Debt Instrument [Line Items]
Repayments of loan	€ 500,000,000	$ 545,000,000