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Debt and Financing Activities - Long-Term Debt (Details)						12 Months Ended
	Nov. 30, 2018 USD ($)	Mar. 26, 2018 USD ($)	Feb. 16, 2018 USD ($)	Feb. 12, 2018 EUR (€)	Feb. 07, 2018 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2018 EUR (€)	Mar. 31, 2017 USD ($)	Mar. 31, 2017 EUR (€)
Debt Instrument [Line Items]
Total debt outstanding						$ 7,595,000,000	$ 7,880,000,000
Proceeds from issuances of long-term debt						1,099,000,000	1,522,000,000		$ 1,824,000,000
Pre-tax loss on debt extinguishment						0	122,000,000		0
Repayments of long-term debt						1,112,000,000	$ 2,287,000,000		1,601,000,000
Future principal payments of long-term debt in 2020						330,000,000
Future principal payments of long-term debt in 2021						1,062,000,000
Future principal payments of long-term debt in 2022						675,000,000
Future principal payments of long-term debt in 2023						801,000,000
Future principal payments of long-term debt in 2024						1,099,000,000
Future principal payments of long-term debt, thereafter						3,628,000,000
Notes
Debt Instrument [Line Items]
Net proceeds from debt			$ 1,500,000,000
1.40% Notes due March 15, 2018
Debt Instrument [Line Items]
Debt interest rate (percent)							1.40%
Repayments of long-term debt							$ 500,000,000
Long-term Debt, Current Maturities
Debt Instrument [Line Items]
Total debt outstanding						330,000,000	1,129,000,000
3.65% Notes due November 30, 2020 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 700,000,000	0
Debt interest rate (percent)						3.65%
3.65% Notes due November 30, 2020 \| Notes Payable
Debt Instrument [Line Items]
Debt interest rate (percent)	3.65%
Aggregate principal amount	$ 700,000,000
4.75% Notes due May 30, 2029 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 400,000,000	0
Debt interest rate (percent)						4.75%
4.75% Notes due May 30, 2029 \| Notes Payable
Debt Instrument [Line Items]
Debt interest rate (percent)	4.75%
Aggregate principal amount	$ 400,000,000
Floating Rate Euro Notes due February 12, 2020 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 280,000,000	337,000,000
Aggregate principal amount \| €				€ 250,000,000
Basis spread on variable rate (percent)				0.15%
1.63% Euro Notes due October 30, 2026 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 560,000,000	669,000,000
Debt interest rate (percent)				1.63%		1.63%
Aggregate principal amount \| €				€ 500,000,000
3.95% Notes due February 16, 2028 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 600,000,000	600,000,000
Debt interest rate (percent)			3.95%			3.95%
Aggregate principal amount			$ 600,000,000
Notes and Debentures Extinguished February 7, 2018 \| Notes
Debt Instrument [Line Items]
Aggregate consideration of debt paid to redeem debt					$ 1,050,000,000
Debt redeemed					$ 936,000,000
Redemption price (percent)					100.00%
Debt premiums					$ 99,000,000
Unpaid interest					20,000,000
Pre-tax loss on debt extinguishment					109,000,000
After-tax loss on debt extinguishment					70,000,000
Amortization of debt premium					99,000,000
Write-off of debt issuance costs					$ 10,000,000
0.63% Euro Notes due August 17, 2021 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 673,000,000	695,000,000
Debt interest rate (percent)						0.63%
4.50% Euro Bonds due April 26, 2017 \| Notes
Debt Instrument [Line Items]
Repayments of long-term debt \| €								€ 500,000,000
4.00% Euro Bonds due October 18, 2016 \| Notes
Debt Instrument [Line Items]
Repayments of long-term debt									$ 385,000,000
4.00% Euro Bonds due October 18, 2016 \| Notes Payable
Debt Instrument [Line Items]
Repayments of long-term debt \| €										€ 350,000,000
5.70% Notes due March 1, 2017 \| Notes
Debt Instrument [Line Items]
Debt interest rate (percent)									5.70%	5.70%
Repayments of long-term debt									$ 500,000,000
1.29% Notes Due March 10, 2017 \| Notes
Debt Instrument [Line Items]
Debt interest rate (percent)									1.29%	1.29%
Repayments of long-term debt									$ 700,000,000
7.50% Notes due February 15, 2019 \| Notes
Debt Instrument [Line Items]
Debt interest rate (percent)		7.50%			7.50%
Aggregate consideration of debt paid to redeem debt		$ 317,000,000
Debt redeemed		$ 302,000,000
Redemption price (percent)		100.00%
Debt premiums		$ 13,000,000
Unpaid interest		2,000,000
Pre-tax loss on debt extinguishment		13,000,000
After-tax loss on debt extinguishment		$ 8,000,000
2.28% Notes due March 15, 2019 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 0	1,100,000,000
Debt interest rate (percent)						2.28%
Repayments of long-term debt						$ 1,100,000,000.0
1.50% Euro Notes due November 17, 2025 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 670,000,000	691,000,000
Debt interest rate (percent)						1.50%
3.13% Sterling Notes due February 17, 2029 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 586,000,000	630,000,000
Debt interest rate (percent)						3.13%
4.75% Notes due March 1, 2021 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 323,000,000	323,000,000
Debt interest rate (percent)					4.75%	4.75%
7.65% Debentures due March 1, 2027 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 167,000,000	167,000,000
Debt interest rate (percent)					7.65%	7.65%
6.00% Notes due March 1, 2041 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 282,000,000	282,000,000
Debt interest rate (percent)					6.00%	6.00%
4.88% Notes due March 15, 2044 \| Notes
Debt Instrument [Line Items]
Total debt outstanding						$ 411,000,000	$ 411,000,000
Debt interest rate (percent)					4.88%	4.88%
Notes Due November 30, 2020 and Notes Due May 30, 2029 \| Notes Payable
Debt Instrument [Line Items]
Proceeds from issuances of long-term debt	$ 1,100,000,000
Redemption price (percent)						101.00%