Employee Benefit Plans - Reclassifications from Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Amortization of actuarial loss - total before tax	$ 743
Tax benefit	(173)	$ (302)	$ (283)
Net of tax	$ 570	$ 508	$ 479

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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-Publisher FASB
-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration