Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net income	$ 14,203	$ 13,866	$ 27,437	$ 26,240
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on investment securities available-for-sale, net of tax expense (benefit) of $(2,714) and $(214) for the three months ended June 30, 2013 and 2012, respectively, and $(2,487) and $255 for the six months ended June 30, 2013 and 2012, respectively	(5,041)	(398)	(4,621)	474
Reclassification adjustment for realized gain on sale of investment securities available-for-sale included in net income, net of tax expense of $4 for the three months ended June 30, 2013 and $300 for the six months ended June 30, 2013	(7)	0	(558)	0
Adjustment for pension and other postretirement benefits, net of tax expense of $332 and $186 for the three months ended June 30, 2013 and 2012, respectively, and $664 and $372 for the six months ended June 30, 2013 and 2012, respectively	617	345	1,233	691
Total other comprehensive income (loss), net of tax	(4,431)	(53)	(3,946)	1,165
Comprehensive income	$ 9,772	$ 13,813	$ 23,491	$ 27,405