Segment Information (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended												12 Months Ended
	Mar. 31, 2019	[1]	Dec. 31, 2018	[1]	Sep. 30, 2018	[1]	Jun. 30, 2018	[1]	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019		Mar. 31, 2018	Mar. 31, 2017
Revenue, Major Customer and Geographic Information [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries	$ 1,238		$ 1,289		$ 1,286		$ 1,137		$ 1,582	$ 1,160	$ 959	$ 1,449	$ 4,950	[1]	$ 5,150	$ 4,845
Entity Wide Revenue By Major Customer Percent Of Revenue Did Not Exceed Ten Percent													10.00%
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member] | Sony [Member]
Revenue, Major Customer and Geographic Information [Line Items]
Entity Wide Revenue By Major Customer Percent Of Revenue													29.00%		27.00%	19.00%
Sales Revenue, Goods, Net [Member] | Customer Concentration Risk [Member] | Microsoft [Member]
Revenue, Major Customer and Geographic Information [Line Items]
Entity Wide Revenue By Major Customer Percent Of Revenue													16.00%		16.00%	17.00%
Switzerland [Member]
Revenue, Major Customer and Geographic Information [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries													$ 2,303		$ 2,272	$ 1,886
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Foreign Countries, Percentage													47.00%		44.00%	39.00%
United States [Member]
Revenue, Major Customer and Geographic Information [Line Items]
Disclosure on Geographic Areas, Revenue from External Customers Attributed to Entity's Country of Domicile													99.00%

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