Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income	$ 22,235	$ 18,664	$ 15,534
Change in securities available-for-sale (AFS):
Unrealized holding gains (losses) on available-for-sale securities arising during the period	(6,309)	2,360	7,404
Reclassification adjustment for (gains) losses realized in income	(97)	(2,139)	(218)
Other-than-temporary impairment losses on AFS securities realized in income	337	5	2
Net unrealized gains (losses)	(6,069)	226	7,188
Income tax effect	2,124	(79)	(2,516)
Net of tax amount	(3,945)	147	4,672
Change in unrealized gain on postretirement benefit:
Net gain (loss) on defined benefit postretirement medical plan realized during the period	287	148	(537)
Net amortization and deferral	46	51	25
Net gain (loss) activity during the period	333	199	(512)
Income tax effect	(117)	(69)	179
Net of tax amount	216	130	(333)
Total other comprehensive income (loss)	(3,729)	277	4,339
Comprehensive income	$ 18,506	$ 18,941	$ 19,873