Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 41,468	$ 34,251	$ 119,475	$ 110,967
Other Comprehensive Income (Loss), net of tax:
Unrealized (loss) gain on securities	(3,580)	7,857	26,285	5,841
Reclassification adjustment for securities gains included in net income	(1)	(1,124)	(666)	(5,388)
Reclassification adjustment for loss on derivative financial instruments included in net income	0	(2,456)	0	(2,456)
Non-credit related unrealized gain on other-than-temporarily impaired debt securities	0	0	0	125
Amortization of unrealized loss on derivative financial instruments	4	3	12	71
Amortization of net unrecognized pension and postretirement items	379	466	877	1,398
Other Comprehensive (Loss) Income	(3,198)	9,658	26,508	4,503
Total Comprehensive Income	$ 38,270	$ 43,909	$ 145,983	$ 115,470