Changes in Accumulated Other Comprehensive Income (Loss) - Balances in Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	$ 41,705
Change in net unrealized holding gains on securities, before reclassification, net of tax expense	27	$ 335
Reclassification for previously unrealized net (gains) losses recognized in income, net of tax expense (benefit)	3	(4)
Balance at end of period	41,617
Net Unrealized Gains (Losses) on Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(520)	107
Change in net unrealized holding gains on securities, before reclassification, net of tax expense	27	335
Reclassification for previously unrealized net (gains) losses recognized in income, net of tax expense (benefit)	3	(4)
Balance at end of period	(490)	438
Pension and Post employment costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(715)	(883)
Balance at end of period	(715)	(883)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period	(1,235)	(776)
Balance at end of period	$ (1,205)	$ (445)