Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net income	$ 16,236	$ 14,203	$ 30,049	$ 27,437
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on investment securities available-for-sale, net of tax expense (benefit) of $909 and $(2,714) for the three months ended June 30, 2014 and 2013, respectively, and $1,766 and $(2,487) for the six months ended June 30, 2014 and 2013, respectively	1,687	(5,041)	3,280	(4,621)
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	0	(7)	0	(558)
Adjustment for pension and other postretirement benefits, net of tax expense (benefit) of $(202) and $332 for the three months ended June 30, 2014 and 2013, respectively, and $(403) and $664 for the six months ended June 30, 2014 and 2013, respectively	(374)	617	(748)	1,233
Total other comprehensive income, net of tax	1,313	(4,431)	2,532	(3,946)
Comprehensive income	$ 17,549	$ 9,772	$ 32,581	$ 23,491