Restructuring and Other Termination Costs (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
	Jan. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	[1]	Jun. 30, 2019	Jun. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and other termination costs, number of positions eliminated, period percent	13.00%
Restructuring and other termination costs		$ 0	$ 0		$ 0	$ 38	[1]
One-time termination benefits
Restructuring Cost and Reserve [Line Items]
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.