Derivative Instruments - Narrative (Details) - USD ($) $ in Millions	5 Months Ended	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2019	Mar. 31, 2018	Oct. 31, 2016	Oct. 31, 2018
Derivative [Line Items]
Cash flow hedge adjustment, net of tax	$ 0	$ (23)	$ 0	$ 0
Interest rate swap
Derivative [Line Items]
Pre-tax impact of gain (loss) on derivatives		(31)
Interest rate swap | Interest expense
Derivative [Line Items]
Gain on cash flow hedge ineffectiveness		5
Designated as hedging instrument | Interest rate swap
Derivative [Line Items]
Foreign currency cash flow hedge gain to be reclassified during next 12 months		6
Designated as hedging instrument | Cash flow hedging | Interest rate swap
Derivative [Line Items]
Derivative notional amount		$ 1,600	$ 1,400		$ 200