Segment Information - Assets and Goodwill by Segment (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Apr. 24, 2017
Segment Reporting Information [Line Items]
Goodwill	$ 1,402	$ 1,310	$ 1,291
Assets, net of AHFS	21,854	21,476
Operating Segments | Eastern Mediterranean
Segment Reporting Information [Line Items]
Goodwill	0	0
Assets, net of AHFS	2,996	2,846
Operating Segments | West Africa
Segment Reporting Information [Line Items]
Goodwill	0	0
Assets, net of AHFS	1,275	1,308
Operating Segments | Other Int'l
Segment Reporting Information [Line Items]
Goodwill	0	0
Assets, net of AHFS	62	114
Operating Segments | United States
Segment Reporting Information [Line Items]
Goodwill	1,291	1,310
Assets, net of AHFS	15,138	15,767
Noble Midstream | United States
Segment Reporting Information [Line Items]
Goodwill	111	0
Assets, net of AHFS	2,280	1,357
Intersegment Eliminations
Segment Reporting Information [Line Items]
Goodwill	0	0
Assets, net of AHFS	(140)	(163)
Corporate
Segment Reporting Information [Line Items]
Goodwill	0	0
Assets, net of AHFS	$ 243	$ 247