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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Summary of Norwegian Kroner (NOK) Denominated Borrowings Outstanding (Detail) kr in Thousands, $ in Thousands	Dec. 31, 2018 USD ($)	Dec. 31, 2018 NOK (kr)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 NOK (kr)
Debt [Line Items]
Amount outstanding	$ 431,456		$ 438,827
Notes Due May 2024
Debt [Line Items]
Amount outstanding	12,200	kr 106,500
Troms Offshore Supply AS \| Notes Due January 2026
Debt [Line Items]
Amount outstanding	22,988	200,000	25,965	kr 212,500
Fair value of debt outstanding	22,988		25,850
Troms Offshore Supply AS \| Notes Due May 2024
Debt [Line Items]
Amount outstanding	12,241	kr 106,500	14,054	kr 115,020
Fair value of debt outstanding	$ 12,239		$ 14,013