| Document and Entity Information | Jan. 17, 2020 |
| Cover [Abstract] | |
| Entity Registrant Name | MCDERMOTT INTERNATIONAL INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000708819 |
| Document Type | 8-K |
| Document Period End Date | Jan. 17, 2020 |
| Entity Incorporation State Country Code | R1 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $1.00 per share |
| Trading Symbol | MDR |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
