Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Income	$ 86,830	$ 62,121	$ 56,808
Other Comprehensive Income (Loss), Net of Tax:
Change in net unrealized gains (losses) on investment securities available-for-sale, net of tax expense (benefit) of $(683), $1,222, and $(3,325) for the years ended December 31, 2015, 2014, and 2013, respectively	(1,269)	2,270	(6,177)
Reclassification adjustment for realized gain on sale of investment securities available-for-sale included in net income, net of tax expense of $221 for the year ended December 31, 2015 and $311 for the year ended December 31, 2013	(409)	0	(577)
Change in adjustment for pension and other postretirement benefits, net of tax benefit (expense) of $(2,746), $7,648, and $(9,344) for the years ended December 31, 2015, 2014, and 2013, respectively	5,099	(14,203)	17,353
Total other comprehensive income (loss), net of tax	3,421	(11,933)	10,599
Comprehensive Income	$ 90,251	$ 50,188	$ 67,407