CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2019		Mar. 31, 2018
Income Statement [Abstract]
Revenues	[1]	$ 2,211		$ 608
Costs and Expenses:
Cost of operations		2,018		476
Project intangibles and inventory-related amortization		10
Total cost of operations		2,028		476
Research and development expenses		8
Selling, general and administrative expenses		72		48
Other intangibles amortization		22
Transaction costs		4		3
Restructuring and integration costs		69		12
Other operating expense, net		1
Total expenses		2,204		539
Income (loss) from investments in unconsolidated affiliates		9		(4)
Investment in unconsolidated affiliates-related amortization		(3)
Operating income		13		65
Other expense:
Interest expense, net		(92)		(12)
Other non-operating income, net		1		2
Total other expense, net		(91)		(10)
(Loss) income before provision for income taxes		(78)		55
Income tax (benefit) expense		(21)		21
Net (loss) income		(57)		34
Less: Net loss attributable to noncontrolling interests		(1)		(1)
Net (loss) income attributable to McDermott		(56)	[2]	35	[3]
Dividends on redeemable preferred stock	[2]	(10)
Accretion of redeemable preferred stock	[2]	(4)
Net (loss) income attributable to common stockholders		$ (70)	[2]	$ 35	[3]
Net (loss) income per share attributable to common stockholders
Basic		$ (0.39)	[2]	$ 0.37	[3]
Diluted		$ (0.39)	[2]	$ 0.37	[3]
Shares used in the computation of net (loss) income per share
Basic		181	[2]	95	[3]
Diluted		181	[2]	95	[3]

[1] Intercompany amounts have been eliminated in consolidation.

[2] ^{The effects of stock-based awards, warrants and redeemable preferred stock were not included in the calculation of diluted earnings per share for the three months ended March 31, 2019 due to the net loss for the period.}

[3] ^{Approximately 0.4 million shares underlying outstanding stock-based awards for the three months ended March 31, 2018 were excluded from the computation of diluted earnings per share during the period 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.}