Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 26, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
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	Portions of the registrant’s Proxy Statement to be filed with the Securities and Exchange Commission pursuant to Regulation 14A under the Securities Exchange Act of 1934 in connection with the registrant’s 2020 Annual Meeting of Stockholders, or an amendment to Form 10-K to be filed not later than 120 days from the end of the registrant’s most recent fiscal year, are incorporated by reference into Part III of this report.