Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Contingency [Line Items]
Effective income tax rate	19.60%	(5.80%)	16.20%	(8.60%)
Foreign earnings not indefinitely reinvested	$ 521		$ 521
Decrease in liability for uncertain tax positions	3
Minimum
Income Tax Contingency [Line Items]
Reasonably possible reduction in liability for uncertain tax positions	34		34
Maximum
Income Tax Contingency [Line Items]
Reasonably possible reduction in liability for uncertain tax positions	39		39
HPES
Income Tax Contingency [Line Items]
Tax indemnification payable, net	6		6
Tax indemnification receivable, uncertain tax positions	44		44
Tax indemnification receivable, tax indemnification payable	91		91
Tax indemnification payable	141		141
Perspecta
Income Tax Contingency [Line Items]
Tax indemnification receivable	92		92
Tax indemnification payable	$ 49		$ 49