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Pension Plans - 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 $ 84 $ 56
Interest cost 333 365
Expected return on plan assets (496) (475)
Recognized net actuarial loss 121 116
Net periodic pension cost $ 42 $ 62