Goodwill and Other Intangible Assets - Schedule of Goodwill (Details) - USD ($) $ in Millions	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Balance at December 31, 2016, gross				$ 10,434
Goodwill impairment				(3,754)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	$ 19,927	$ 19,927	$ 6,680
Goodwill, acquisition			13,052
Goodwill, currency exchange and others		(48)	195
Goodwill, net, ending balance		20,790	19,927
Operating segments | Oilfield Services
Goodwill [Line Items]
Balance at December 31, 2016, gross				2,779
Goodwill impairment				(2,633)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	13,205	13,205	146
Goodwill, acquisition			13,052
Goodwill, currency exchange and others		3	7
Goodwill, purchase accounting adjustments		(154)
Goodwill, net, ending balance		13,054	13,205
Operating segments | Oilfield Equipment
Goodwill [Line Items]
Balance at December 31, 2016, gross				3,852
Goodwill impairment				(867)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	3,034	3,034	2,985
Goodwill, acquisition			0
Goodwill, currency exchange and others		(16)	49
Goodwill, purchase accounting adjustments		242
Goodwill, net, ending balance		3,260	3,034
Operating segments | Turbomachinery & Process Solutions
Goodwill [Line Items]
Balance at December 31, 2016, gross				1,814
Goodwill impairment				0
Goodwill [Roll Forward]
Goodwill, net, beginning balance	1,906	1,906	1,814
Goodwill, acquisition			0
Goodwill, currency exchange and others		(24)	92
Goodwill, purchase accounting adjustments		394
Goodwill, net, ending balance		2,276	1,906
Operating segments | Digital Solutions
Goodwill [Line Items]
Balance at December 31, 2016, gross				1,989
Goodwill impairment				$ (254)
Goodwill [Roll Forward]
Goodwill, net, beginning balance	1,782	1,782	1,735
Goodwill, acquisition			0
Goodwill, currency exchange and others		(11)	47
Goodwill, purchase accounting adjustments		429
Goodwill, net, ending balance		2,200	$ 1,782
GE Transaction Agreement
Goodwill [Roll Forward]
Goodwill, purchase accounting adjustments	$ 911
GE Transaction Agreement | Operating segments
Goodwill [Roll Forward]
Goodwill, acquisition		13,963
GE Transaction Agreement | Operating segments | Oilfield Services
Goodwill [Roll Forward]
Goodwill, acquisition		$ 12,898