Restructuring (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Accrued restructuring severance and exit costs activity
Accrued beginning balance	$ 12	$ 19	$ 49
Accrued ending balance	7	12	19
Employee Severance
Accrued restructuring severance and exit costs activity
Accrued beginning balance	1	3	28
Expense	0	0	0
Change in estimate	0	(1)	(3)
Payments	(1)	(1)	(22)
Accretion and other	0	0	0
Accrued ending balance	0	1	3
Facility Exit
Accrued restructuring severance and exit costs activity
Accrued beginning balance	11	16	21
Expense	0	0	0
Change in estimate	0	0	0
Payments	(3)	(4)	(5)
Accretion and other	(1)	(1)	0
Accrued ending balance	$ 7	$ 11	$ 16