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Commitment and Contingencies (Repairs to U.S. Flagged Vessels Operating Abroad) - Additional Information (Detail)	6 Months Ended	9 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Percentage of vessel repair duty	50.00%	50.00%

X

- Definition

Percentage of custom duty for vessel repair.

+ References

No definition available.

+ Details

Name:	tdw_PercentageOfCustomDutyForVesselRepair
Namespace Prefix:	tdw_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration