Restructuring Costs - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 104	$ 74	$ 441	$ 248
Fiscal 2020 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring costs			3
Cost incurred to date	295		295
Fiscal 2020 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring costs			7
Cost incurred to date	278		278
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			(5)
Cost incurred to date	477		477
Fiscal 2019 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring costs			(2)
Cost incurred to date	336		336
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	987		987
Fiscal 2018 Plan | Employee Severance
Restructuring Cost and Reserve [Line Items]
Cost incurred to date	791		791
Fiscal 2018 Plan | Facilities Costs
Restructuring Cost and Reserve [Line Items]
Cost incurred to date	$ 196		$ 196