Accrued Liabilities - Summary of Accrued Liabilities (Parenthetical) (Detail)	Sep. 30, 2018
Accrued Liabilities Current [Abstract]
Maxumum percentage of individual current liabilities	5.00%

Maxumum percentage of individual current liabilities.

No definition available.

Name:	mdr_MaxumumPercentageOfIndividualCurrentLiabilities
Namespace Prefix:	mdr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant