Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net Income	$ 73,063	$ 26,047
Other Comprehensive (Loss) Income, net of tax:
Unrealized (loss) gain on securities	(39,999)	17,431
Reclassification adjustment for securities gains included in net income	377	(36)
Amortization of net unrealized losses on AFS securities transferred to HTM	1,787	795
Net unrealized loss on interest rate swaps used in cash flow hedges	(1,707)	0
Amortization of net unrecognized pension and postretirement income	289	255
Other Comprehensive (Loss) Income	(39,253)	18,445
Total Comprehensive Income	$ 33,810	$ 44,492