Restructuring Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 465	$ 789	$ 238
Restructuring Reserve [Abstract]
Accrued expenses and other current liabilities	273	367
Other long-term liabilities	106	153
Total	379	520
Fiscal 2018 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(44)	826
Restructuring Reserve [Abstract]
Total	94	355	0
Restructuring cost incurred to date	782
Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	(32)
Restructuring Reserve [Abstract]
Total	7	22	161
Restructuring cost incurred to date	216
Workforce Reductions | Fiscal 2018 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(30)	624
Restructuring Reserve [Abstract]
Total	59	257	0
Restructuring cost incurred to date	594
Workforce Reductions | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	(32)
Restructuring Reserve [Abstract]
Total	7	19	155
Restructuring cost incurred to date	207
Facilities Costs | Fiscal 2018 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(14)	202
Restructuring Reserve [Abstract]
Total	35	98	0
Restructuring cost incurred to date	188
Facilities Costs | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	0
Restructuring Reserve [Abstract]
Total	0	$ 3	$ 6
Restructuring cost incurred to date	$ 9