Employee Benefit Plans - Reclassifications from Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2018
Retirement Benefits [Abstract]
Amortization of actuarial loss - total before tax	$ 186	$ 372
Tax benefit	(44)	(89)
Net of tax	$ 142	$ 283

Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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Period Type:	duration