Commitments and Contingent Liabilities - Additional Information (Detail) kr in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) Bond Agreement	Dec. 31, 2017 SEK (kr)
Commitments And Contingent Liabilities [Line Items]
Outstanding standby and commercial letters of credit \| $	$ 22,576
Percentage on employees covered by collective bargaining agreements	39.00%	39.00%
Bargaining agreement beginning expiration year	2018-05
Bargaining agreement ending expiration year	2020-09
Number of collective bargaining agreements \| Agreement	9
Collective Bargaining Agreement Two [Member]
Commitments And Contingent Liabilities [Line Items]
Percentage of covered employees	54.00%
Collective Bargaining Agreement One [Member]
Commitments And Contingent Liabilities [Line Items]
Percentage of covered employees	19.00%
Akers AB [Member]
Commitments And Contingent Liabilities [Line Items]
Number of surety bonds issued \| Bond	2
Amount covered by guarantees	$ 4,000	kr 33,900

Bargaining agreement beginning expiration year.

No definition available.

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- Definition

Bargaining agreement ending expiration year.

+ References

No definition available.

+ Details

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- Definition

Commitments And Contingent Liabilities [Line Items]

+ References

No definition available.

+ Details

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- Definition

Number of collective bargaining agreements.

+ References

No definition available.

+ Details

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- Definition

Number of surety bonds issued.

+ References

No definition available.

+ Details

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- Definition

Percentage of covered employees under collective bargaining agreements.

+ References

No definition available.

+ Details

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- Definition

Sum of the amount of expected guaranteed benefits in excess of the projected account balances for minimum guaranteed benefit contracts, as of the balance sheet date, net of reinsurance recoverables, for all guaranteed benefit types.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 80
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6484115&loc=d3e19393-158473

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=6588021&loc=d3e7104-158389

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of employee participants subject to a collective bargaining arrangement to all participants in a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

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- Details

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