Face (par) amount of debt instrument at time of issuance.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Description of the frequency of periodic payments (monthly, quarterly, annual).

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

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Weighted average interest rate of debt outstanding.

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Amount of cash restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

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Summary of Debt Outstanding (Parenthetical) (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Jan. 31, 2019
Debt [Line Items]
Restricted cash	$ 6,975,000	$ 25,953,000
Troms Offshore Supply AS
Debt [Line Items]
Description of frequency of periodic payments on notes	semi-annually
Weighted average interest rate of debt borrowings	5.00%
Troms Offshore Supply AS \| Level 2
Debt [Line Items]
Fair value of debt outstanding	$ 80,600,000	$ 81,500,000
8.00% Senior Secured Notes Due August 2022
Debt [Line Items]
Debt instrument interest rate	8.00%	8.00%
Debt Instrument Maturity Period	August 2022	August 2022
8.00% Senior Secured Notes Due August 2022 \| Offer \| Maximum
Debt [Line Items]
Aggregate principal amount		$ 25,400,000
8.00% Senior Secured Notes Due August 2022 \| Level 2
Debt [Line Items]
Fair value of debt outstanding	$ 360,400,000	$ 359,400,000
Norwegian Kroner Denominated Notes Due May 2024 \| Troms Offshore Supply AS
Debt [Line Items]
Debt Instrument Maturity Period	May 2024	May 2024
Norwegian Kroner Denominated Notes Due January 2026 \| Troms Offshore Supply AS
Debt [Line Items]
Debt Instrument Maturity Period	January 2026	January 2026
United States Dollar Denominated Notes Due January 2027 \| Troms Offshore Supply AS
Debt [Line Items]
Debt Instrument Maturity Period	January 2027	January 2027
United States Dollar Denominated Notes Due April 2027 \| Troms Offshore Supply AS
Debt [Line Items]
Debt Instrument Maturity Period	April 2027	April 2027
Tendered Notes
Debt [Line Items]
Aggregate principal amount			$ 160,000