Stockholders' Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ 4,278,672	$ 3,853,436	$ 4,127,636	$ 3,803,661
Reclassification of net loss realized and included in earnings	9,668	14,148	19,083	27,725
Amortization of unrealized net loss on securities transferred to HTM	387	390	792	818
Income tax (expense) benefit	(13,181)	1,393	(41,393)	10,785
Balance	4,365,419	3,920,718	4,365,419	3,920,718
Accumulated Other Comprehensive Loss Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(473,679)	(450,748)
Net change in unrealized gain (loss)			146,860	(59,111)
Income tax (expense) benefit			(34,140)	13,450
Balance	(360,959)	(496,409)	(360,959)	(496,409)
Held to Maturity Securities Transferred from AFS [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(8,071)	(9,385)
Amortization of unrealized net loss on securities transferred to HTM			792	818
Income tax (expense) benefit			(196)	(184)
Balance	(7,475)	(8,751)	(7,475)	(8,751)
Employee Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(77,235)	(103,061)
Reclassification of net loss realized and included in earnings			1,888	2,254
Valuation adjustments to employee benefit plans				22,014
Income tax (expense) benefit			(594)	(5,453)
Balance	(75,941)	(84,246)	(75,941)	(84,246)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(514,972)	(653,515)	(606,092)	(621,127)
Net change in unrealized gain (loss)			157,783	(98,151)
Reclassification of net loss realized and included in earnings			19,083	27,725
Valuation adjustments to employee benefit plans				22,014
Amortization of unrealized net loss on securities transferred to HTM			792	818
Income tax (expense) benefit			(41,393)	10,785
Balance	(469,827)	(657,936)	(469,827)	(657,936)
Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			(47,136)	(58,306)
Net change in unrealized gain (loss)			11,096	(38,696)
Reclassification of net loss realized and included in earnings			17,195	25,471
Income tax (expense) benefit			(6,463)	2,972
Balance	(25,308)	(68,559)	(25,308)	(68,559)
Equity Method Investment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			29	373
Net change in unrealized gain (loss)			(173)	(344)
Balance	$ (144)	$ 29	$ (144)	$ 29