Restructuring Costs - Restructuring Liability (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Restructuring Reserve [Roll Forward]
Costs Expensed, net of reversals	$ 142	$ 185
Restructuring Liability, ending balance	327
Fiscal 2020 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0
Adoption of ASC 842	0
Costs Expensed, net of reversals	153
Costs Not Affecting Restructuring Liability	(15)
Cash Paid	(28)
Other	2
Restructuring Liability, ending balance	112
Fiscal 2020 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0
Adoption of ASC 842	0
Costs Expensed, net of reversals	148
Costs Not Affecting Restructuring Liability	(10)
Cash Paid	(28)
Other	2
Restructuring Liability, ending balance	112
Fiscal 2020 Plan | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0
Adoption of ASC 842	0
Costs Expensed, net of reversals	5
Costs Not Affecting Restructuring Liability	(5)
Cash Paid
Other	0
Restructuring Liability, ending balance	0
Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	206
Adoption of ASC 842	(53)
Costs Expensed, net of reversals	1
Costs Not Affecting Restructuring Liability	1
Cash Paid	(47)
Other	0
Restructuring Liability, ending balance	108
Costs reversed	4
Fiscal 2019 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	138
Adoption of ASC 842	0
Costs Expensed, net of reversals	1
Costs Not Affecting Restructuring Liability	1
Cash Paid	(43)
Other	(1)
Restructuring Liability, ending balance	96
Fiscal 2019 Plan | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	68
Adoption of ASC 842	(53)
Costs Expensed, net of reversals	0
Costs Not Affecting Restructuring Liability	0
Cash Paid	(4)
Other	1
Restructuring Liability, ending balance	12
Fiscal 2018 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	94
Adoption of ASC 842	(36)
Costs Expensed, net of reversals	(10)
Costs Not Affecting Restructuring Liability	0
Cash Paid	(13)
Other	2
Restructuring Liability, ending balance	37
Costs reversed	11
Fiscal 2018 Plan | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	59
Adoption of ASC 842	0
Costs Expensed, net of reversals	(9)
Costs Not Affecting Restructuring Liability	0
Cash Paid	(11)
Other	(2)
Restructuring Liability, ending balance	37
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
Other Prior Year Plans
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	10
Adoption of ASC 842	(1)
Costs Expensed, net of reversals	(2)
Costs Not Affecting Restructuring Liability	0
Cash Paid	(1)
Other	(2)
Restructuring Liability, ending balance	4
Costs reversed	2
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	(2)
Costs Not Affecting Restructuring Liability	0
Cash Paid	(1)
Other	(2)
Restructuring Liability, ending balance	4
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
Acquired Liabilities
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	69
Adoption of ASC 842	0
Costs Expensed, net of reversals	0
Costs Not Affecting Restructuring Liability	0
Cash Paid	(3)
Other	0
Restructuring Liability, ending balance	66
Acquired Liabilities | Workforce Reductions
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	51
Adoption of ASC 842	0
Costs Expensed, net of reversals	0
Costs Not Affecting Restructuring Liability	0
Cash Paid	(3)
Other	1
Restructuring Liability, ending balance	49
Acquired Liabilities | Facilities Costs
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	18
Adoption of ASC 842	0
Costs Expensed, net of reversals	0
Costs Not Affecting Restructuring Liability	0
Cash Paid
Other	(1)
Restructuring Liability, ending balance	$ 17