Segment Information (Net Revenue By Geographic Area) (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
Revenue from External Customer [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
North America [Member]
Revenue from External Customer [Line Items]
Net revenue									2,270	1,906	2,090
International [Member]
Revenue from External Customer [Line Items]
Net revenue									$ 3,267	$ 3,044	$ 3,060