Contractual interest rate for funds borrowed, under the debt agreement.

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Debt and Financing Activities - Other Information (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Debt Instrument [Line Items]
Future principal payments of long-term debt in 2017	$ 1,612
Future principal payments of long-term debt in 2018	1,092
Future principal payments of long-term debt in 2019	1,458
Future principal payments of long-term debt in 2020	3
Future principal payments of long-term debt in 2021	2
Future principal payments of long-term debt, thereafter	3,980
Repayments of loan	1,598	$ 353	$ 348
Total debt outstanding	8,147	9,709
Floating Rate Notes
Debt Instrument [Line Items]
Repayments of loan	400
Total debt outstanding	0	$ 400
6.50% Notes Due February 15 2014
Debt Instrument [Line Items]
Repayments of loan			$ 350
Debt interest rate			6.50%
0.95% Notes Due December 4 2015
Debt Instrument [Line Items]
Repayments of loan	$ 500
Debt interest rate	0.95%
3.25% Notes Due March 1 2016
Debt Instrument [Line Items]
Repayments of loan	$ 600
Debt interest rate	3.25%