Nature of Operations and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Vessel	Dec. 31, 2018 Vessel	Jan. 01, 2019 USD ($)
Property, Plant and Equipment [Line Items]
Extended useful life, months	30 months
Inspection interval	The majority of our vessels require certification inspections twice in every five year period
Number of Offshore Supply Vessels	217	257
Number of Vessels Disposed	40
Number Of Assets Held For Sale	46
Number of Vessel Sold	40
Right of use assets | $	$ 4,338
Lease liabilities | $	$ 4,775
Accounting Standards Update 2016-02
Property, Plant and Equipment [Line Items]
Right of use assets | $			$ 5,000
Lease liabilities | $			$ 5,400
Marine Equipment
Property, Plant and Equipment [Line Items]
Percentage of salvage values	7.50%
Remaining Number Of Vessels
Property, Plant and Equipment [Line Items]
Remaining Number Of Vessels	171
Actively Employed Vessels
Property, Plant and Equipment [Line Items]
Remaining Number Of Vessels	152
Stacked Vessels
Property, Plant and Equipment [Line Items]
Number Of Assets Held For Sale	46
Remaining Number Of Vessels	19
Minimum | Marine Equipment | From Date of Construction
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	10 years
Minimum | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	3 years
Maximum
Property, Plant and Equipment [Line Items]
Highly liquid investments, maturities	3 months
Maximum | Marine Equipment | From Date of Construction
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	20 years
Maximum | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives, years	10 years