Restructuring Costs - Restructuring Liability (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Reserve [Roll Forward]
Costs Expensed, Net of Reversals	$ 265	$ 32	$ 337	$ 174
Restructuring Liability, ending balance	365		365
Fiscal 2021 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			0
Costs Expensed, Net of Reversals			353
Costs Not Affecting Restructuring Liability			(8)
Cash Paid			(95)
Other			0
Restructuring Liability, ending balance	250		250
Fiscal 2021 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			0
Costs Expensed, Net of Reversals			340
Costs Not Affecting Restructuring Liability			(4)
Cash Paid			(89)
Other			0
Restructuring Liability, ending balance	247		247
Fiscal 2021 Plan | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			0
Costs Expensed, Net of Reversals			13
Costs Not Affecting Restructuring Liability			(4)
Cash Paid			(6)
Other			0
Restructuring Liability, ending balance	3		3
Fiscal 2020 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			76
Costs Expensed, Net of Reversals			(9)
Costs Not Affecting Restructuring Liability			6
Cash Paid			(40)
Other			4
Restructuring Liability, ending balance	37		37
Costs reversed			11
Fiscal 2020 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			74
Costs Expensed, Net of Reversals			(5)
Costs Not Affecting Restructuring Liability			2
Cash Paid			(38)
Other			4
Restructuring Liability, ending balance	37		37
Fiscal 2020 Plan | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			2
Costs Expensed, Net of Reversals			(4)
Costs Not Affecting Restructuring Liability			4
Cash Paid			(2)
Other			0
Restructuring Liability, ending balance	0		0
Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			30
Costs Expensed, Net of Reversals			(6)
Costs Not Affecting Restructuring Liability			0
Cash Paid			(9)
Other			2
Restructuring Liability, ending balance	17		17
Costs reversed			10
Fiscal 2019 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			25
Costs Expensed, Net of Reversals			(3)
Costs Not Affecting Restructuring Liability			(2)
Cash Paid			(9)
Other			1
Restructuring Liability, ending balance	12		12
Fiscal 2019 Plan | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			5
Costs Expensed, Net of Reversals			(3)
Costs Not Affecting Restructuring Liability			2
Cash Paid			0
Other			1
Restructuring Liability, ending balance	5		5
Other Prior Year Plans
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			24
Costs Expensed, Net of Reversals			0
Costs Not Affecting Restructuring Liability			3
Cash Paid			(11)
Other			2
Restructuring Liability, ending balance	18		18
Costs reversed			3
Other Prior Year Plans | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			24
Costs Expensed, Net of Reversals			0
Costs Not Affecting Restructuring Liability			3
Cash Paid			(11)
Other			2
Restructuring Liability, ending balance	18		18
Other Prior Year Plans | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			0
Costs Expensed, Net of Reversals			0
Costs Not Affecting Restructuring Liability			0
Cash Paid			0
Other			0
Restructuring Liability, ending balance	0		0
Acquired Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			50
Costs Expensed, Net of Reversals			(1)
Costs Not Affecting Restructuring Liability			1
Cash Paid			(5)
Other			(2)
Restructuring Liability, ending balance	43		43
Acquired Liabilities | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			39
Costs Expensed, Net of Reversals			0
Costs Not Affecting Restructuring Liability			0
Cash Paid			(3)
Other			0
Restructuring Liability, ending balance	36		36
Acquired Liabilities | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			11
Costs Expensed, Net of Reversals			(1)
Costs Not Affecting Restructuring Liability			1
Cash Paid			(2)
Other			(2)
Restructuring Liability, ending balance	$ 7		$ 7