Pension and Other Postretirement Benefits - Additional Information (Detail) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2017 RetirementPlans Pension_Plan	Jun. 30, 2016 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Employer non-elective contributions, percentage of employee compensation		3.00%
Curtailment gain | $	$ 887		$ 887
Akers AB [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Number of postretirement benefit plans | RetirementPlans		2
U.S. Defined Benefit Pension Plans [Member] | Akers AB [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Number of defined benefit pension plans		2
Foreign Defined Benefits Pension Plans [Member] | Akers AB [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Number of defined benefit pension plans		2