Business Combination - Summary of Pro Forma Financial Information (Detail) - Chicago Bridge & Iron Company N.V. [Member] - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2018	[1]	Jun. 30, 2017	Jun. 30, 2018	[1]	Jun. 30, 2017
Business Acquisition [Line Items]
Pro forma revenue		$ 2,492		$ 2,072	$ 4,845		$ 4,419
Pro forma net income (loss) attributable to McDermott		$ 63		$ (315)	$ 112		$ (334)
Pro forma net income (loss) per share attributable to McDermott:
Basic		$ 0.44		$ (2.19)	$ 0.78		$ (2.32)
Diluted		$ 0.44		$ (2.19)	$ 0.78		$ (2.32)
Basic	[2]	144		144	144		144
Diluted		144		144	144		144

[1] Adjustments, net of tax, included in the pro forma net income above were of a non-recurring nature and totaled $94 million and $109 million for the three and six months ended June 30, 2018, respectively. The adjustments reflect the elimination of restructuring and integration costs ($54 million and $62 million), transaction costs ($29 million and $36 million) and debt extinguishment costs ($11 million and $11 million) that were included in McDermott and CB&I’s historical results for the three and six months ended June 30, 2018, respectively. These pro forma results exclude the effect of adjustments to the opening balance sheet associated with fair value purchase accounting judgments.

[2] Pro forma net income (loss) per share was calculated using basic and diluted shares outstanding as of June 30, 2018.