Stockholders' Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ 80,069	$ (53,935)	$ 80,069
Net change in unrealized gain or loss	$ (203,551)	$ 50,135	(95,355)	(594,455)	(95,355)
Reclassification of net income or loss realized and included in earnings	(5,570)	(3,198)		(9,408)	(2,912)
Valuation adjustments to pension plan attributable to VERIP and curtailment					59,606
Other valuation adjustments to employee benefit plans				(7,987)	(10,651)
Amortization of unrealized net gain or loss on securities transferred to HTM	266	(45)		527	(101)
Income tax expense (benefit)	(48,941)	21,542		(138,081)	(12,206)
Ending Balance	(527,177)	42,862		(527,177)	42,862
Accumulated Other Comprehensive Loss Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			171,224	11,037	171,224
Net change in unrealized gain or loss				(547,636)	(96,045)
Reclassification of net income or loss realized and included in earnings				1,707	2,166
Transfer of net unrealized loss from AFS to HTM securities portfolio				15,405
Income tax expense (benefit)				(119,739)	(21,095)
Ending Balance	(399,748)	98,440		(399,748)	98,440
Held to Maturity Securities Transferred from AFS [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			276	153	276
Transfer of net unrealized loss from AFS to HTM securities portfolio				(15,405)
Amortization of unrealized net gain or loss on securities transferred to HTM				527	(101)
Income tax expense (benefit)				(3,358)	(23)
Ending Balance	(11,367)	198		(11,367)	198
Employee Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(125,573)	(80,946)	(125,573)
Reclassification of net income or loss realized and included in earnings				1,652	3,445
Valuation adjustments to pension plan attributable to VERIP and curtailment					59,606
Other valuation adjustments to employee benefit plans				(7,987)	(10,651)
Income tax expense (benefit)				(1,430)	11,774
Ending Balance	(85,851)	(84,947)		(85,851)	(84,947)
Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			39,511	16,284	39,511
Net change in unrealized gain or loss				(47,287)	(252)
Reclassification of net income or loss realized and included in earnings				(12,767)	(12,991)
Income tax expense (benefit)				(13,554)	(2,862)
Ending Balance	(30,216)	29,634		(30,216)	29,634
Equity Method Investment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ (5,369)	(463)	(5,369)
Net change in unrealized gain or loss				468	438
Reclassification of net income or loss realized and included in earnings					4,468
Ending Balance	$ 5	$ (463)		$ 5	$ (463)