Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	5 Months Ended	12 Months Ended
	Dec. 31, 2018	Mar. 31, 2017	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Oct. 31, 2016	Oct. 31, 2015
Income Tax Contingency [Line Items]
Income tax refunds receivable				$ 90
Refund received	$ 72
Effective tax rate		39.00%		36.00%	(5.00%)	38.00%
Deferred tax assets				$ 13	$ 0
Federal net operating loss carryforwards				308
Net operating loss carryforwards				27
Unrecognized tax benefits		$ 8		52	8	$ 7	$ 7
Unrecognized tax benefits decrease		$ 0		2	0	$ 0
Interest expense, net				$ 9	$ 1
Scenario, Forecast
Income Tax Contingency [Line Items]
Unrecognized tax benefits decrease			$ 18