Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Effective income tax rate	44.20%	29.10%	54.50%	(11.50%)
Foreign earnings not indefinitely reinvested	$ 547		$ 547
Potential federal and state tax cost	410		410
Decrease in liability for uncertain tax positions	13
Reasonably possible reduction in liability for uncertain tax positions	37		37
HPES
Income Tax Contingency [Line Items]
Tax indemnification payable, net	3		3
Tax indemnification receivable, uncertain tax positions	48		48
Tax indemnification receivable, tax indemnification payable	79		79
Tax indemnification payable	130		130
Perspecta
Income Tax Contingency [Line Items]
Tax indemnification payable	44		44
Tax indemnification receivable	$ 81		$ 81