Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Statement of Other Comprehensive Income [Abstract]
Net Income	$ 13,106	$ 11,625	$ 39,346	$ 31,846
Other Comprehensive Income (loss), Net of Tax:
Net unrealized gains (losses) on investment securities available-for-sale, net of tax expense (benefit) of $491 and $(100) for the three months ended September 30, 2012 and 2011, respectively, and $746 and $139 for the nine months ended September 30, 2012 and 2011, respectively	911	(185)	1,385	259
Adjustment for pension and other postretirement benefits, net of tax expense of $187 and $63 for the three months ended September 30, 2012 and 2011, respectively, and $559 and $189 for the nine months ended September 30, 2012 and 2011, respectively	347	117	1,038	351
Total other comprehensive income (loss), net of tax	1,258	(68)	2,423	610
Comprehensive Income	$ 14,364	$ 11,557	$ 41,769	$ 32,456