Restructuring Costs - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 265	$ 32	$ 337	$ 174
Fiscal 2020 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs			(9)
Cost incurred to date	283		283
Fiscal 2020 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring costs			(5)
Cost incurred to date	266		266
Fiscal 2020 Plan | Facilities Costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs			(4)
Cost incurred to date	17		17
Fiscal 2019 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs			(6)
Cost incurred to date	476		476
Fiscal 2019 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring costs			(3)
Cost incurred to date	335		335
Fiscal 2019 Plan | Facilities Costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs			(3)
Cost incurred to date	141		141
Fiscal 2018 Plan
Restructuring Cost and Reserve [Line Items]
Cost incurred to date	986		986
Fiscal 2018 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Cost incurred to date	790		790
Fiscal 2018 Plan | Facilities Costs
Restructuring Cost and Reserve [Line Items]
Cost incurred to date	$ 196		$ 196