Restructuring - Restructuring Liability (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	$ 0
Costs Expensed	3
Cash Paid	(3)
Restructuring Liability, ending balance	0	$ 0
Fiscal 2018 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	7
Costs Expensed	0
Cash Paid	(3)
Restructuring Liability, ending balance	4	7
Fiscal 2017 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	7	0
Costs Expensed		14
Cash Paid		(7)
Restructuring Liability, ending balance		7
Workforce reductions | Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0
Costs Expensed	1
Cash Paid	(1)
Restructuring Liability, ending balance	0	0
Workforce reductions | Fiscal 2018 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	1
Costs Expensed	0
Cash Paid	(1)
Restructuring Liability, ending balance	0	1
Workforce reductions | Fiscal 2017 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	1	0
Costs Expensed		6
Cash Paid		(5)
Restructuring Liability, ending balance		1
Facilities costs | Fiscal 2019 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	0
Costs Expensed	2
Cash Paid	(2)
Restructuring Liability, ending balance	0	0
Facilities costs | Fiscal 2018 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	6
Costs Expensed	0
Cash Paid	(2)
Restructuring Liability, ending balance	4	6
Facilities costs | Fiscal 2017 Plan
Restructuring Reserve [Roll Forward]
Restructuring Liability, beginning balance	$ 6	0
Costs Expensed		8
Cash Paid		(2)
Restructuring Liability, ending balance		$ 6