Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net Income	$ 39,750	$ 36,680	$ 78,007	$ 76,716
Other Comprehensive Income (Loss), net of tax:
Unrealized gain (loss) on securities	12,839	(12,008)	29,865	(2,016)
Reclassification adjustment for securities gains included in net income	(49)	(1,569)	(665)	(4,264)
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	34	8	68
Amortization of net unrecognized pension and postretirement items	32	466	498	932
Other Comprehensive Income (Loss)	12,826	(13,077)	29,706	(5,155)
Total Comprehensive Income	$ 52,576	$ 23,603	$ 107,713	$ 71,561