Business Combination - Additional Information (Detail) - USD ($) $ in Millions			12 Months Ended
	May 10, 2018		Dec. 31, 2018	Dec. 31, 2017	Dec. 18, 2017
Business Acquisition [Line Items]
Number of equity shares issued for business acquisition			85,000,000
Business combination, ownership percentage					53.00%
Business combination, net of cash acquired	$ 4,100		$ 2,374
Estimated fair value of the net tangible and identifiable intangible assets acquired recorded as goodwill			2,654
Initial purchase price allocation adjustments to acquired contracts			278
Outstanding RPOs			10,913	$ 3,901
Chicago Bridge & Iron Company N.V. [Member]
Business Acquisition [Line Items]
Business Acquisition, Date of acquisition agreement	Dec. 18, 2017
Business acquisition, combination date	May 10, 2018
Business combination, Consideration	$ 2,870
Number of equity shares issued for business acquisition	84,500,000
Business combination, number of McDermott's shares entitled for each share of CB&I owned	85
Business combination, number of converted shares acquired	2,200,000
Business combination, Gross purchase price	$ 4,565
Business combination, net of cash acquired	4,067
Estimated fair value of the net tangible and identifiable intangible assets acquired recorded as goodwill	4,822	[1]	4,800
Initial purchase price allocation adjustments to acquired contracts	273		1,200
Increase in goodwill due to adjustments			1,000
Outstanding RPOs	$ 8,300
Business combination revenue recognized			4,400
Business combination operating income recognized			43
Business combination, goodwill impairment			2,200
Business combination, restructuring and integration costs			61
Transaction costs			$ 48
Chicago Bridge & Iron Company N.V. [Member] | Effect of Reverse Stock Split [Member]
Business Acquisition [Line Items]
Business combination, number of McDermott's shares entitled for each share of CB&I owned	0.82407

[1] Goodwill resulted from the acquired established workforce, which does not qualify for separate recognition, as well as expected future cost savings and revenue synergies associated with the combined operations. Of the $4.8 billion of estimated goodwill recorded in conjunction with the Combination, $1.7 billion is deductible for tax purposes. See Note 9, Goodwill and Other Intangible Assets, for our allocation of goodwill by reporting segment and discussion of impairment charges recorded during the fourth quarter of 2018.