Cover Page - USD ($) $ in Billions	12 Months Ended
Cover Page - USD ($) $ in Billions	Dec. 31, 2019	Mar. 31, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K/A
Amendment Flag	true
Amendment Description	McDermott International, Inc. (“McDermott,” “we,” “us” or “our”) is filing this Amendment No. 1 on Form 10-K/A (this “Amendment”) to amend our annual report on Form 10-K for the year ended December 31, 2019, originally filed with the Securities and Exchange Commission (“SEC”) on February 28, 2020 (the “Original Filing” or “our Form 10-K”), solely for the purpose of including the information required by Part III of Form 10-K because we do not intend to file a definitive proxy statement for a 2020 Annual Meeting of Stockholders before the date that is 120 days after our fiscal year end. In accordance with Rule 12b-15 under the Securities and Exchange Act of 1934, as amended (the “Exchange Act”), Part III, Items 10 through 14 of the Original Filing are hereby amended and restated in their entirety, and Part IV, Item 15 of the Original Filing is hereby amended and restated in its entirety, with the only changes being the addition of new certifications by our principal executive officer and principal financial officer filed herewith. This Amendment does not amend or otherwise update any other information in the Original Filing. Accordingly, this Amendment should be read in conjunction with the Original Filing and with our filings with the SEC subsequent to the Original Filing. Bankruptcy Proceedings under Chapter 11 As previously disclosed, on January 21, 2020, McDermott and certain of its subsidiaries (together with McDermott, the “Debtors”) filed voluntary petitions under Chapter 11 (“Chapter 11”) of the United States Bankruptcy Code (the “Bankruptcy Code”) in the United States Bankruptcy Court for the Southern District of Texas (the “Bankruptcy Court”) to pursue a Joint Prepackaged Chapter 11 Plan of Reorganization. The Chapter 11 Cases are being jointly administered under the caption In re McDermott International, Inc., et al., No. 20-30336. On March 12, 2020, the Bankruptcy Court entered the Order Approving the Debtors’ Disclosure Statement and Confirming the Second Amended Joint Prepackaged Chapter 11 Plan of Reorganization (Technical Modifications) of McDermott International, Inc. and its Debtor Affiliates [Docket No. 665] (the “Confirmation Order”), which approved and confirmed the Second Amended Joint Prepackaged Chapter 11 Plan of Reorganization (Technical Modifications) of McDermott International, Inc. and Its Debtor Affiliates [Docket No. 651] (the “Plan of Reorganization”). The Debtors expect that the effective date of the Plan of Reorganization will occur as soon as all conditions precedent to the Plan of Reorganization have been satisfied (the “Effective Date”). Although the Debtors are expecting the occurrence of the Effective Date as soon as reasonably practicable, the Debtors can make no assurance as to when, or ultimately if, the Plan of Reorganization will become effective. It is also possible that amendments could be made to the Plan of Reorganization prior to the Effective Date.
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	MDRIQ
Entity Registrant Name	McDERMOTT INTERNATIONAL, INC.
Entity Central Index Key	0000708819
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		193,081,224
Entity Public Float			$ 1.8
Entity File Number	001-08430
Entity Tax Identification Number	72-0593134
Entity Address, Address Line One	757 N. Eldridge Parkway
Entity Address, City or Town	HOUSTON
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77079
City Area Code	(281)
Local Phone Number	870-5000
Entity Incorporation, State or Country Code	R1
Document Annual Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, $1.00 par value
Documents Incorporated by Reference	The following documents (or parts thereof) are incorporated by reference into the following parts of this Form 10-K: none.

MCDERMOTT INTERNATIONAL INC 10-K/A