Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 39,559	$ 59,779	$ 65,606	$ 116,442
Other Comprehensive Income, net of tax:
Unrealized gain on securities	34,424	24,917	51,853	45,215
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	793	1,021	1,589	1,995
Non-credit related unrealized loss on other-than-temporarily impaired debt securities	0	(600)	0	(682)
Amortization of net unrecognized pension and postretirement income	255	275	510	566
Other Comprehensive Income	33,131	25,476	51,576	46,906
Total Comprehensive Income	$ 72,690	$ 85,255	$ 117,182	$ 163,348