Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Consolidated Statements of Comprehensive Income [Abstract]
Net Income	$ 13,866	$ 11,033	$ 26,240	$ 20,221
Other Comprehensive Income, Net of Tax:
Net unrealized gains (losses) on investment securities available-for-sale, net of tax expense (benefit) of $(214) and $586 for the three months ended June 30, 2012 and 2011, respectively, and $255 and $239 for the six months ended June 30, 2012 and 2011, respectively	(398)	1,087	474	444
Adjustment for pension and other postretirement benefits, net of tax expense of $186 and $63 for the three months ended June 30, 2012 and 2011, respectively, and $372 and $126 for the six months ended June 30, 2012 and 2011, respectively	345	117	(691)	(234)
Total other comprehensive income, net of tax	(53)	1,204	1,165	678
Comprehensive Income	$ 13,813	$ 12,237	$ 27,405	$ 20,899