Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 5,022	$ 6,657
Available-for-sale investment securities:
Gross unrealized holding gain arising in the period	457	(1,063)
Related tax expense	(160)	372
Less: reclassification adjustment for net gain included in net income	418	3,163
Related tax expense on reclassification adjustment	(146)	(1,107)
Net effect on other comprehensive income (loss)	25	(2,747)
Defined benefit plans:
Amortization of unrecognized loss and service cost on pension plan	45	38
Related tax expense on amortization	(16)	(13)
Net effect on other comprehensive income (loss)	29	25
Total other comprehensive income (loss), net of tax	54	(2,722)
Total comprehensive income	$ 5,076	$ 3,935