CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Income Statement [Abstract]
Revenues	[1]	$ 6,705,000,000		$ 2,985,000,000		$ 2,636,000,000
Costs and Expenses:
Cost of operations		6,104,000,000		2,449,000,000		2,249,000,000
Project intangibles and inventory-related amortization		83,000,000
Total cost of operations		6,187,000,000		2,449,000,000		2,249,000,000
Research and development expenses		20,000,000		5,000,000
Selling, general and administrative expenses		282,000,000		204,000,000		183,000,000
Other intangibles amortization		62,000,000
Transaction costs		48,000,000		9,000,000
Restructuring and integration costs		134,000,000		0		11,000,000
Goodwill impairment	[2]	2,168,000,000
Other asset impairments		58,000,000		1,000,000		55,000,000
Other operating expense (income), net		3,000,000		(2,000,000)
Total expenses		8,962,000,000		2,666,000,000		2,498,000,000
Income (loss) from investments in unconsolidated affiliates		13,000,000		(12,000,000)
Investment in unconsolidated affiliates-related amortization		(12,000,000)
Operating (loss) income		(2,256,000,000)		307,000,000		138,000,000
Other expense:
Interest expense, net		(259,000,000)		(63,000,000)		(59,000,000)
Other non-operating (expense) income, net		(56,000,000)		5,000,000		3,000,000
Total other expense, net		(315,000,000)		(58,000,000)		(56,000,000)
(Loss) income before provision for income taxes		(2,571,000,000)		249,000,000		82,000,000
Income tax expense		104,000,000		69,000,000		42,000,000
Non-operating loss from investments in unconsolidated affiliates		(3,000,000)		(2,000,000)		(4,000,000)
Net (loss) income		(2,678,000,000)		178,000,000		36,000,000
Less: Net income (loss) attributable to noncontrolling interests		9,000,000		(1,000,000)		2,000,000
Net (loss) income attributable to McDermott		(2,687,000,000)	[3]	179,000,000	[4]	34,000,000	[4]
Dividends on redeemable preferred stock	[3]	(3,000,000)
Accretion of redeemable preferred stock	[3]	(1,000,000)
Net (loss) income attributable to common stockholders		$ (2,691,000,000)	[3]	$ 179,000,000	[4]	$ 34,000,000	[4]
Net (loss) income per share attributable to common stockholders
Basic		$ (17.94)	[3]	$ 1.97	[4]	$ 0.43	[4]
Diluted		$ (17.94)	[3]	$ 1.88	[4]	$ 0.36	[4]
Shares used in the computation of net (loss) income per share
Basic		150	[3]	91	[4]	80	[4]
Diluted		150	[3]	95	[4]	95	[4]

[1] Intercompany amounts have been eliminated in consolidation.

[2] Represents impairment of goodwill associated with our NCSA, EARC, APAC and Technology reporting units, resulting from our impairment assessment during the fourth quarter of 2018. See Note 9, Goodwill and Other Intangible Assets, for further discussion. The goodwill impairment values are included within the applicable operating group’s Operating loss.

[3] The effects of restricted stock, warrants and redeemable preferred stock were not included in the calculation of diluted earnings per share for 2018 due to the net loss for the period.

[4] Approximately 0.5 million and 0.7 million shares underlying outstanding stock-based awards in 2017 and 2016 were excluded from the computation of diluted earnings per share during those periods because the exercise price of those awards was greater than the average market price of our common stock, and the inclusion of such shares would have been antidilutive in each of those years.