Restructuring Costs - Restructuring Liability (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	$ 180
Costs Expensed, Net of Reversals	551	$ 252	$ 465
Restructuring Liability, ending balance	270	180
Fiscal 2021 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0
Costs Expensed, Net of Reversals	538
Costs Not Affecting Restructuring Liability	(28)
Cash Paid	(327)
Other	0
Restructuring Liability, ending balance	183	0
Fiscal 2020 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	76	0
Costs Expensed, Net of Reversals	4	292
Costs Not Affecting Restructuring Liability	5	(14)
Cash Paid	(62)	(193)
Other	4	(9)
Restructuring Liability, ending balance	27	76	0
Costs reversed and adjustments	11
Fiscal 2020 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		0
Restructuring Liability, ending balance			0
Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	30	206
Costs Expensed, Net of Reversals	(3)	(25)
Costs Not Affecting Restructuring Liability	(1)	(1)
Cash Paid	(18)	(90)
Other	5	(7)
Restructuring Liability, ending balance	13	30	206
Costs reversed and adjustments	9	30
Fiscal 2019 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		(53)
Restructuring Liability, ending balance			(53)
Fiscal 2018 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	20	94
Costs Expensed, Net of Reversals		(11)
Costs Not Affecting Restructuring Liability		0
Cash Paid		(31)
Other		4
Restructuring Liability, ending balance		20	94
Costs reversed and adjustments		11
Fiscal 2018 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		(36)
Restructuring Liability, ending balance			(36)
Other Prior Year Plans
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	24
Costs Expensed, Net of Reversals	12
Costs Not Affecting Restructuring Liability	(7)
Cash Paid	(19)
Other	2
Restructuring Liability, ending balance	12	24
Costs reversed and adjustments	3
Other Prior Year Plans
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	4	10
Costs Expensed, Net of Reversals		(1)
Costs Not Affecting Restructuring Liability		0
Cash Paid		(3)
Other		(1)
Restructuring Liability, ending balance		4	10
Costs reversed and adjustments		3
Other Prior Year Plans | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		(1)
Restructuring Liability, ending balance			(1)
Acquired Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	50	69
Costs Expensed, Net of Reversals	0	(3)
Costs Not Affecting Restructuring Liability	1	0
Cash Paid	(16)	(17)
Other	0	1
Restructuring Liability, ending balance	35	50	69
Acquired Liabilities | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		0
Restructuring Liability, ending balance			0
Workforce Reductions | Fiscal 2021 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0
Costs Expensed, Net of Reversals	501
Costs Not Affecting Restructuring Liability	(11)
Cash Paid	(313)
Other	3
Restructuring Liability, ending balance	180	0
Workforce Reductions | Fiscal 2020 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	74	0
Costs Expensed, Net of Reversals	8	271
Costs Not Affecting Restructuring Liability	1	(11)
Cash Paid	(60)	(177)
Other	4	(9)
Restructuring Liability, ending balance	27	74	0
Costs reversed and adjustments	14
Workforce Reductions | Fiscal 2020 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		0
Restructuring Liability, ending balance			0
Workforce Reductions | Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	25	138
Costs Expensed, Net of Reversals	(1)	(25)
Costs Not Affecting Restructuring Liability	(2)	0
Cash Paid	(17)	(83)
Other	2	(5)
Restructuring Liability, ending balance	7	25	138
Workforce Reductions | Fiscal 2019 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		0
Restructuring Liability, ending balance			0
Workforce Reductions | Fiscal 2018 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	20	59
Costs Expensed, Net of Reversals		(10)
Costs Not Affecting Restructuring Liability		0
Cash Paid		(29)
Other		0
Restructuring Liability, ending balance		20	59
Workforce Reductions | Fiscal 2018 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		0
Restructuring Liability, ending balance			0
Workforce Reductions | Other Prior Year Plans
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	24
Costs Expensed, Net of Reversals	12
Costs Not Affecting Restructuring Liability	(7)
Cash Paid	(19)
Other	2
Restructuring Liability, ending balance	12	24
Workforce Reductions | Other Prior Year Plans
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	4	9
Costs Expensed, Net of Reversals		(1)
Costs Not Affecting Restructuring Liability		0
Cash Paid		(3)
Other		(1)
Restructuring Liability, ending balance		4	9
Workforce Reductions | Other Prior Year Plans | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		0
Restructuring Liability, ending balance			0
Workforce Reductions | Acquired Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	39	51
Costs Expensed, Net of Reversals	1	1
Costs Not Affecting Restructuring Liability	0	0
Cash Paid	(7)	(16)
Other	1	3
Restructuring Liability, ending balance	34	39	51
Workforce Reductions | Acquired Liabilities | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		0
Restructuring Liability, ending balance			0
Facilities Costs | Fiscal 2021 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0
Costs Expensed, Net of Reversals	37
Costs Not Affecting Restructuring Liability	(17)
Cash Paid	(14)
Other	(3)
Restructuring Liability, ending balance	3	0
Facilities Costs | Fiscal 2020 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	2	0
Costs Expensed, Net of Reversals	(4)	21
Costs Not Affecting Restructuring Liability	4	(3)
Cash Paid	(2)	(16)
Other	0	0
Restructuring Liability, ending balance	0	2	0
Facilities Costs | Fiscal 2020 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		0
Restructuring Liability, ending balance			0
Facilities Costs | Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	5	68
Costs Expensed, Net of Reversals	(2)	0
Costs Not Affecting Restructuring Liability	1	(1)
Cash Paid	(1)	(7)
Other	3	(2)
Restructuring Liability, ending balance	6	5	68
Facilities Costs | Fiscal 2019 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		(53)
Restructuring Liability, ending balance			(53)
Facilities Costs | Fiscal 2018 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0	35
Costs Expensed, Net of Reversals		(1)
Costs Not Affecting Restructuring Liability		0
Cash Paid		(2)
Other		4
Restructuring Liability, ending balance		0	35
Facilities Costs | Fiscal 2018 Plan | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		(36)
Restructuring Liability, ending balance			(36)
Facilities Costs | Other Prior Year Plans
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
Facilities Costs | Other Prior Year Plans
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0	1
Costs Expensed, Net of Reversals		0
Costs Not Affecting Restructuring Liability		0
Cash Paid		0
Other		0
Restructuring Liability, ending balance		0	1
Facilities Costs | Other Prior Year Plans | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		(1)
Restructuring Liability, ending balance			(1)
Facilities Costs | Acquired Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	11	18
Costs Expensed, Net of Reversals	(1)	(4)
Costs Not Affecting Restructuring Liability	1	0
Cash Paid	(9)	(1)
Other	(1)	(2)
Restructuring Liability, ending balance	$ 1	11	18
Facilities Costs | Acquired Liabilities | Adoption of ASC 842
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance		$ 0
Restructuring Liability, ending balance			$ 0