Comprehensive Income - Schedule of Accumulated Other Comprehensive Income Component Details (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Securities available-for-sale:
Net securities gains reclassified into earnings	$ (170)	$ (113)	$ (248)	$ (129)
Related income tax expense	63	42	91	47
Net effect on accumulated other comprehensive income for the period	(107)	(71)	(157)	(82)
Securities held-to-maturity:
Amortization of unrealized gain transferred from available-for-sale	(132)	(362)	(270)	(650)
Related income tax expense	48	133	99	244
Net effect on accumulated other comprehensive income for the period	(84)	(229)	(171)	(406)
Defined benefit pension plan:
Amortization of net loss and prior service costs	378	909	752	1,743
Related income tax expense	(139)	(334)	(277)	(693)
Net effect on accumulated other comprehensive income for the period	239	575	475	1,050
Total reclassifications for the period	$ 48	$ 275	$ 147	$ 562