Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 06, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Trading Symbol	MDRIQ
Entity Registrant Name	McDERMOTT INTERNATIONAL, INC.
Entity Central Index Key	0000708819
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
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 Common Stock, Shares Outstanding		193,081,224
Entity Incorporation, State or Country Code	R1
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, par value $1.00 per share