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Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Compensation And Retirement Disclosure [Abstract]        
Service cost $ 327 $ 305 $ 930 $ 912
Interest cost 158 182 448 542
Expected return on plan assets (329) (266) (935) (796)
Amortization of actuarial losses 80 44 228 132
Net periodic pension cost $ 236 $ 265 $ 671 $ 790