Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 21,860	$ 20,046	$ 19,039
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	1,572	(25,909)	5,854
Less: reclassification adjustment for gains included in net income	(450)	(3,019)	(1,843)
Total unrealized gains (losses) on securities	1,122	(28,928)	4,011
Accretion of net unrealized losses transferred during period	3,188	1,886
Pension liability adjustment:
Net (loss) gain	(8,544)	4,932	(2,488)
Amortization of prior service cost and loss included in net periodic benefit cost	226	694	649
Total pension liability adjustment	(8,318)	5,626	(1,839)
Other comprehensive (loss) income	(4,008)	(21,416)	2,172
Comprehensive income (loss)	$ 17,852	$ (1,370)	$ 21,211