Restructuring Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 252	$ 465	$ 789
Restructuring Reserve [Abstract]
Accrued expenses and other current liabilities	145	273
Other long-term liabilities	35	106
Total	180	379
Fiscal 2019 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(25)	507
Restructuring Reserve [Abstract]
Total	30	206	0
Restructuring cost incurred to date	482
Fiscal 2018 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(11)	(44)
Restructuring Reserve [Abstract]
Total	20	94	355
Restructuring cost incurred to date	771
Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs		0
Restructuring Reserve [Abstract]
Total		7	22
Restructuring cost incurred to date	215
Workforce Reductions | Fiscal 2019 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(25)	363
Restructuring Reserve [Abstract]
Total	25	138	0
Restructuring cost incurred to date	338
Workforce Reductions | Fiscal 2018 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(10)	(30)
Restructuring Reserve [Abstract]
Total	20	59	257
Restructuring cost incurred to date	584
Workforce Reductions | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs		0
Restructuring Reserve [Abstract]
Total		7	19
Restructuring cost incurred to date	206
Facilities Costs | Fiscal 2019 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	144
Restructuring Reserve [Abstract]
Total	5	68	0
Restructuring cost incurred to date	144
Facilities Costs | Fiscal 2018 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(1)	(14)
Restructuring Reserve [Abstract]
Total	0	35	98
Restructuring cost incurred to date	187
Facilities Costs | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs		0
Restructuring Reserve [Abstract]
Total		$ 0	$ 3
Restructuring cost incurred to date	$ 9