Restructuring Costs - Restructuring Liability (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Costs Expensed, net of reversals	$ 74	$ 76	$ 248	$ 418
Restructuring Liability, ending balance	242		242
Fiscal 2020 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			0
Adoption of ASC 842			0
Costs Expensed, net of reversals			275
Costs Not Affecting Restructuring Liability			(21)
Cash Paid			(150)
Other			1
Restructuring Liability, ending balance	105		105
Fiscal 2020 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			0
Adoption of ASC 842			0
Costs Expensed, net of reversals			252
Costs Not Affecting Restructuring Liability			(11)
Cash Paid			(139)
Other			1
Restructuring Liability, ending balance	103		103
Fiscal 2020 Plan | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			0
Adoption of ASC 842			0
Costs Expensed, net of reversals			23
Costs Not Affecting Restructuring Liability			(10)
Cash Paid			(11)
Other			0
Restructuring Liability, ending balance	2		2
Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			206
Adoption of ASC 842			(53)
Costs Expensed, net of reversals			(16)
Costs Not Affecting Restructuring Liability			(4)
Cash Paid			(76)
Other			1
Restructuring Liability, ending balance	58		58
Costs reversed			19
Fiscal 2019 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			138
Adoption of ASC 842			0
Costs Expensed, net of reversals			(15)
Costs Not Affecting Restructuring Liability			(3)
Cash Paid			(70)
Other			0
Restructuring Liability, ending balance	50		50
Fiscal 2019 Plan | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			68
Adoption of ASC 842			(53)
Costs Expensed, net of reversals			(1)
Costs Not Affecting Restructuring Liability			(1)
Cash Paid			(6)
Other			1
Restructuring Liability, ending balance	8		8
Fiscal 2018 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			94
Adoption of ASC 842			(36)
Costs Expensed, net of reversals			(8)
Costs Not Affecting Restructuring Liability			0
Cash Paid			(30)
Other			5
Restructuring Liability, ending balance	25		25
Costs reversed			10
Fiscal 2018 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			59
Adoption of ASC 842			0
Costs Expensed, net of reversals			(7)
Costs Not Affecting Restructuring Liability			0
Cash Paid			(28)
Other			1
Restructuring Liability, ending balance	25		25
Fiscal 2018 Plan | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			35
Adoption of ASC 842			(36)
Costs Expensed, net of reversals			(1)
Costs Not Affecting Restructuring Liability			0
Cash Paid			(2)
Other			4
Restructuring Liability, ending balance	0		0
Other Prior Year Plans
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			10
Adoption of ASC 842			(1)
Costs Expensed, net of reversals			(1)
Costs Not Affecting Restructuring Liability			0
Cash Paid			(2)
Other			0
Restructuring Liability, ending balance	6		6
Costs reversed			3
Other Prior Year Plans | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			9
Adoption of ASC 842			0
Costs Expensed, net of reversals			(1)
Costs Not Affecting Restructuring Liability			0
Cash Paid			(2)
Other			0
Restructuring Liability, ending balance	6		6
Other Prior Year Plans | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			1
Adoption of ASC 842			(1)
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			69
Adoption of ASC 842			0
Costs Expensed, net of reversals			(2)
Costs Not Affecting Restructuring Liability			0
Cash Paid			(15)
Other			(4)
Restructuring Liability, ending balance	48		48
Acquired Liabilities | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			51
Adoption of ASC 842			0
Costs Expensed, net of reversals			3
Costs Not Affecting Restructuring Liability			0
Cash Paid			(14)
Other			(1)
Restructuring Liability, ending balance	39		39
Acquired Liabilities | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance			18
Adoption of ASC 842			0
Costs Expensed, net of reversals			(5)
Costs Not Affecting Restructuring Liability			0
Cash Paid			(1)
Other			(3)
Restructuring Liability, ending balance	$ 9		$ 9