Schedule of Aggregate Amount of Senior Unsecured Notes Outstanding (Detail) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2017	Dec. 31, 2017
Debt [Line Items]
Amount outstanding		$ 448,160
Predecessor
Debt [Line Items]
Amount outstanding	$ 2,040,525
September 2013 Senior Unsecured Notes \| Predecessor
Debt [Line Items]
Fair value of debt outstanding	280,000
Aggregate debt outstanding	$ 500,000
Weighted average remaining life in years	6 years 4 months 24 days
Weighted average coupon rate on notes outstanding	4.86%
August 2011 Senior Unsecured Notes \| Predecessor
Debt [Line Items]
Fair value of debt outstanding	$ 92,400
Aggregate debt outstanding	$ 165,000
Weighted average remaining life in years	3 years 7 months 6 days
Weighted average coupon rate on notes outstanding	4.42%
September 2010 Senior Unsecured Notes \| Predecessor
Debt [Line Items]
Fair value of debt outstanding	$ 214,200
Aggregate debt outstanding	$ 382,500
Weighted average remaining life in years	3 years 1 month 6 days
Weighted average coupon rate on notes outstanding	4.35%
Troms Offshore Supply AS \| May 2015 notes
Debt [Line Items]
Amount outstanding		25,463
Fair value of debt outstanding		25,427
Troms Offshore Supply AS \| May 2015 notes \| Predecessor
Debt [Line Items]
Amount outstanding	$ 27,421
Fair value of debt outstanding	27,395
Troms Offshore Supply AS \| March 2015 notes
Debt [Line Items]
Amount outstanding		23,345
Fair value of debt outstanding		$ 23,251
Troms Offshore Supply AS \| March 2015 notes \| Predecessor
Debt [Line Items]
Amount outstanding	24,573
Fair value of debt outstanding	$ 24,544

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+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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