Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net income	$ 16,767	$ 14,993	$ 46,816	$ 42,430
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on investment securities available-for-sale, net of tax expense (benefit) of $(615) and $(392) for the three months ended September 30, 2014 and 2013, respectively, and $1,150 and $(2,879) for the nine months ended September 30, 2014 and 2013, respectively	(1,144)	(726)	2,136	(5,347)
Reclassification adjustment for realized gain on sale of investment securities available-for-sale included in net income, net of tax expense of $300 for the nine months ended September 30, 2013	0	0	0	(558)
Adjustment for pension and other postretirement benefits, net of tax expense (benefit) of $(201) and $332 for the three months ended September 30, 2014 and 2013, respectively, and $(604) and $996 for the nine months ended September 30, 2014 and 2013, respectively	(374)	616	(1,122)	1,849
Total other comprehensive income (loss), net of tax	(1,518)	(110)	1,014	(4,056)
Comprehensive income	$ 15,249	$ 14,883	$ 47,830	$ 38,374