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Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Compensation And Retirement Disclosure [Abstract]    
Service cost $ 308 $ 297
Interest cost 187 143
Expected return on plan assets (399) (299)
Amortization of actuarial losses 64 73
Net periodic pension cost $ 160 $ 214