Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 38,257	$ 40,036
Other Comprehensive Income, net of tax:
Unrealized gain on securities	17,026	9,992
Reclassification adjustment for securities gains included in net income	(616)	(2,695)
Non-credit related unrealized gain on other-than-temporarily impaired debt securities	0	125
Amortization of unrealized loss on derivative financial instruments	4	34
Amortization of net unrecognized pension and postretirement items	466	466
Other Comprehensive Income	16,880	7,922
Total Comprehensive Income	$ 55,137	$ 47,958