Segment Information (Net Revenue By Timing Recognition) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting, Revenue Reconciling Item [Line Items]
Net revenue	$ 1,387	$ 1,593	$ 1,348	$ 1,209	$ 1,238	$ 1,289	$ 1,286	$ 1,137	$ 5,537	$ 4,950	$ 5,150
Recognized at a point in time
Segment Reporting, Revenue Reconciling Item [Line Items]
Net revenue									2,043	1,902
Recognized over time
Segment Reporting, Revenue Reconciling Item [Line Items]
Net revenue									$ 3,494	$ 3,048