Retirement Plans - Components of Net Periodic Pension Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 0	$ 0	$ 0
Interest cost	679	689	604
Expected return on plan assets	1,178	1,090	1,088
Net amortization and deferral	(380)	(326)	(270)
Net periodic pension cost (benefit)	(119)	(75)	(214)
Net loss (gain) recognized in other comprehensive loss	(322)	448	412
Total recognized in net periodic benefit cost and other comprehensive loss (before tax)	$ (441)	$ 373	$ 198

No definition available.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

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Amount, before tax, after reclassification adjustment, of (increase) decrease in accumulated other comprehensive income from prior service cost (credit) of defined benefit plan.

+ References

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-Publisher FASB
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Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of net periodic benefit cost (credit) for defined benefit plan.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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