CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Revenues	[1]	$ 958,531	$ 558,543	$ 2,266,635	$ 1,994,202
Costs and Expenses:
Cost of operations		773,910	455,430	1,852,949	1,666,775
Research and development expenses		1,657	69	2,958	199
Selling, general and administrative expenses		55,671	46,983	142,280	137,386
Other operating (income) expenses, net		221	13,006	(1,808)	53,806
Total costs and expenses		831,459	515,488	1,996,379	1,858,166
Operating income		127,072	43,055	270,256	136,036
Other expense:
Interest expense, net		(11,976)	(17,431)	(50,886)	(41,324)
Other non-operating income (expense), net		803	5,237	(1,074)	(1,005)
Total other expense, net		(11,173)	(12,194)	(51,960)	(42,329)
Income before provision for income taxes		115,899	30,861	218,296	93,707
Provision for income taxes		19,532	15,976	53,221	55,110
Income before income (loss) from Investments in Unconsolidated Affiliates		96,367	14,885	165,075	38,597
Income (loss) from Investments in Unconsolidated Affiliates		(3,441)	1,507	(11,495)	(2,844)
Net income		92,926	16,392	153,580	35,753
Less: Net income (loss) attributable to noncontrolling interest		(1,775)	284	550	1,160
Net income attributable to McDermott International, Inc.		$ 94,701	$ 16,108	$ 153,030	$ 34,593
Net income per share attributable to McDermott International, Inc.:
Basic		$ 0.33	$ 0.07	$ 0.57	$ 0.14
Diluted		$ 0.33	$ 0.06	$ 0.54	$ 0.12
Shares used in the computation of net income per share:
Basic		283,991,161	240,899,888	269,720,153	240,093,169
Diluted		285,774,621	283,907,353	284,859,710	283,132,920

[1] Intersegment transactions included in revenues were not significant for all the periods presented.