Stockholders' Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (621,127)	$ (772,182)
Net change in unrealized gain (loss)	(77,799)	100,944
Reclassification of net loss realized and included in earnings	13,577	9,520
Valuation adjustments to employee benefit plans	22,014	(1,836)
Amortization of unrealized net loss on securities transferred to HTM	428	494
Income tax (expense) benefit	9,392	(24,405)
Ending Balance	(653,515)	(687,465)
Accumulated Other Comprehensive Loss Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(450,748)	(584,408)
Net change in unrealized gain (loss)	(48,264)	80,958
Income tax (expense) benefit	10,927	(18,224)
Ending Balance	(488,085)	(521,674)
Held to Maturity Securities Transferred from AFS [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9,385)	(10,734)
Amortization of unrealized net loss on securities transferred to HTM	428	494
Income tax (expense) benefit	(96)	(111)
Ending Balance	(9,053)	(10,351)
Employee Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(103,061)	(97,952)
Reclassification of net loss realized and included in earnings	1,019	1,519
Valuation adjustments to employee benefit plans	22,014	(1,836)
Income tax (expense) benefit	(5,176)	71
Ending Balance	(85,204)	(98,198)
Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(58,306)	(79,093)
Net change in unrealized gain (loss)	(29,191)	19,280
Reclassification of net loss realized and included in earnings	12,558	8,001
Income tax (expense) benefit	3,737	(6,141)
Ending Balance	(71,202)	(57,953)
Equity Method Investment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	373	5
Net change in unrealized gain (loss)	(344)	706
Ending Balance	$ 29	$ 711