Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 2,517	$ 4,824	$ 12,460	$ 16,511
Available-for-sale investment securities:
Gross unrealized holding gain arising in the period	(876)	(107)	(17,146)	1,468
Related tax expense	307	37	6,001	(514)
Less: reclassification adjustment for net gain included in net income	(1)	112	443	3,275
Related tax expense on reclassification adjustment	0	(39)	(155)	(1,146)
Net effect on other comprehensive income (loss)	(568)	(143)	(11,433)	(1,175)
Defined benefit plans:
Net loss arising during the period	3,023	0	3,023	318
Related tax benefit	(1,058)	0	(1,058)	(111)
Amortization of unrecognized loss and service cost on pension plan	50	41	149	119
Related tax expense on amortization	(17)	(14)	(52)	(41)
Recognition of loss due to settlement and curtailment	264	0	264	353
Related tax expense	(92)	0	(92)	(124)
Net effect on other comprehensive income (loss)	(2,170)	(27)	(2,234)	(514)
Total other comprehensive income (loss), net of tax	1,602	(116)	(9,199)	(661)
Total comprehensive income	$ 4,119	$ 4,708	$ 3,261	$ 15,850