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Restructuring and Other Termination Costs Narrative (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jan. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and other termination costs, number of positions eliminated, period percent	13.00%
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				$ 0
Initial restructuring recognition on January 30, 2018		$ 0	$ 0	38	$ 0
Termination benefits paid				(38)
Restructuring reserve, ending balance		$ 0		0
One-time termination benefits [Member]
Restructuring Reserve [Roll Forward]
Initial restructuring recognition on January 30, 2018	$ 38			$ 38