Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 10,252	$ 9,753	$ 29,183	$ 27,728
Net unrealized holding gain (loss) on securities available for sale	1,461	6,113	(27,793)	13,564
Reclassification adjustments for net gain recognized in income	0	(666)	(1,434)	(1,398)
Tax effect	(583)	(2,172)	11,654	(4,851)
Net unrealized gain (loss) on securities available for sale	878	3,275	(17,573)	7,315
Amortization of net actuarial loss	117	99	350	293
Amortization of prior service credit	(66)	(66)	(197)	(197)
Tax effect	(21)	(14)	(61)	(39)
Amortization of net actuarial loss and prior service credit on pension and postretirement plans, net of tax	30	19	92	57
Other comprehensive income (loss), net of tax	908	3,294	(17,481)	7,372
Comprehensive income	$ 11,160	$ 13,047	$ 11,702	$ 35,100