Restructuring Costs - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 72	$ 142
Fiscal 2020 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(5)
Cost incurred to date	287
Fiscal 2020 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(1)
Cost incurred to date	270
Fiscal 2020 Plan | Facilities Costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(4)
Cost incurred to date	17
Fiscal 2019 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(5)
Cost incurred to date	477
Fiscal 2019 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(2)
Cost incurred to date	336
Fiscal 2019 Plan | Facilities Costs
Restructuring Cost and Reserve [Line Items]
Restructuring costs	(3)
Cost incurred to date	141
Fiscal 2018 Plan
Restructuring Cost and Reserve [Line Items]
Cost incurred to date	985
Fiscal 2018 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Cost incurred to date	789
Fiscal 2018 Plan | Facilities Costs
Restructuring Cost and Reserve [Line Items]
Cost incurred to date	$ 196