Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 43,380	$ 38,257
Other Comprehensive Income, net of tax:
Unrealized gain on securities	4,273	17,026
Reclassification adjustment for securities gains included in net income	(719)	(616)
Amortization of unrealized loss on derivative financial instruments	0	4
Amortization of net unrecognized pension and postretirement items	343	466
Other Comprehensive Income	3,897	16,880
Total Comprehensive Income	$ 47,277	$ 55,137