Restructuring and Other Termination Costs Narrative (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 30, 2018	Mar. 31, 2019	Mar. 31, 2018	[1]
Restructuring Cost and Reserve [Line Items]
Restructuring and other termination costs, number of positions eliminated, period percent	13.00%
Restructuring Reserve [Roll Forward]
Restructuring and other termination costs		$ 0	$ 38
One-time termination benefits
Restructuring Reserve [Roll Forward]
Restructuring and other termination costs		$ 38

[1] Financial information for 2018 has been recast to reflect the retrospective application of the successful efforts method of accounting. See Note 1.