Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 4,134	$ 4,179	$ 8,358	$ 12,439
Available-for-sale investment securities:
Gross unrealized holding gain (loss) arising in the period	7,171	(395)	9,458	15,503
Related tax (expense) benefit	(2,509)	139	(3,309)	(5,426)
Less: reclassification adjustment for net gain included in net income	62	124	673	160
Related tax expense	(22)	(43)	(236)	(56)
Net effect on other comprehensive income (loss)	4,622	(337)	5,712	9,973
Defined benefit plans:
Net (loss) income arising during the period	(167)	(311)	340	(1,490)
Related tax benefit (expense)	58	109	(119)	522
Amortization of unrecognized loss and service cost on benefit plans	26	32	88	97
Related tax expense	(9)	(11)	(30)	(34)
Recognition of loss due to settlement and curtailment	82	361	454	1,383
Related tax expense	(29)	(126)	(159)	(484)
Net effect on other comprehensive (loss) income	(39)	54	574	(6)
Total other comprehensive income (loss), net of tax (expense) benefit	4,583	(283)	6,286	9,967
Total comprehensive income	$ 8,717	$ 3,896	$ 14,644	$ 22,406