Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 59,779	$ 35,197	$ 116,442	$ 84,677
Other Comprehensive Income (Loss), net of tax:
Unrealized gain (loss) on securities	24,917	(6,631)	45,215	(34,275)
Reclassification adjustment for securities gains included in net income	(137)	(3)	(188)	(19)
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	1,021	0	1,995	0
Non-credit related unrealized (loss) gain on other-than-temporarily impaired debt securities	(600)	8	(682)	232
Amortization of net unrecognized pension and postretirement income	275	540	566	879
Other Comprehensive Income (Loss)	25,476	(6,086)	46,906	(33,183)
Total Comprehensive Income	$ 85,255	$ 29,111	$ 163,348	$ 51,494