Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 275,497	$ 178,040	$ 226,339
Unrealized gains (losses) on AFS investment securities:
Unrealized (loss)/gain on securities	(17,948)	65,651	56,919
Reclassification adjustment for securities gains included in net income	(25,905)	(2,359)	(3,686)
Amortization of net unrealized losses on AFS securities transferred to HTM	2,690	3,448	6,285
Non-credit related unrealized (loss) gain on other-than-temporarily impaired debt securities	0	0	(680)
Net unrealized gains (losses) on AFS investment securities	(41,163)	66,740	58,838
Net unrealized holding (losses) gains arising during the period	(2,147)	0	0
Reclassification adjustment for net loss realized in net income on interest rate swaps used in cash flow hedges	2,670	0	0
Net unrealized (losses) gains on interest rate swaps used in cash flow hedges	(4,817)	0	0
Defined benefit pension plan and postretirement benefits:
Unrecognized pension and postretirement (cost) income	7,144	(2,532)	(937)
Amortization of net unrecognized pension and postretirement income	1,156	1,020	1,025
Net unrealized (losses) gains on defined benefit pension and postretirement plans	8,300	(1,512)	88
Other Comprehensive (Loss)/Income	(37,680)	65,228	58,926
Total Comprehensive Income	$ 237,817	$ 243,268	$ 285,265