Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($)	3 Months Ended				9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019		Sep. 30, 2018		Dec. 31, 2018	Dec. 31, 2017
Accumulated other comprehensive income (loss)	$ 144,173,000		$ (141,596,000)		$ 144,173,000		$ (141,596,000)		$ (64,669,000)	$ 14,108,000
Other Comprehensive Income Before Reclassifications					274,744,000		(168,551,000)
Reclassified from Accumulated Oher Comprehensive Income					3,710,000		1,463,000
Other Comprehensive Income (Loss), before Tax					278,454,000		(167,088,000)
Other Comprehensive Income (Loss), Tax					(69,612,000)		41,772,000
Other comprehensive income (loss), net of tax	35,275,000		(32,815,000)		208,842,000		(125,316,000)
Reclassification Where Impairment Was Not Previously Recognized					0		0
Unrealized Gain Loss on Securities OTTI [Member]
Accumulated other comprehensive income (loss)	3,464,000	[1]	4,113,000	[1]	3,464,000	[1]	4,113,000	[1]	3,861,000	3,411,000
Other Comprehensive Income Before Reclassifications					(709,000)		(102,000)
Reclassified from Accumulated Oher Comprehensive Income					133,000		68,000
Other Comprehensive Income (Loss), before Tax					(576,000)		(34,000)
Other Comprehensive Income (Loss), Tax					144,000		9,000
Other comprehensive income (loss), net of tax					(432,000)		(25,000)
Reclassification Where Impairment Was Not Previously Recognized					35,000		12,000
Unrealized Gain Loss on Securities Other [Member]
Accumulated other comprehensive income (loss)	119,108,000	[1]	(122,089,000)	[1]	119,108,000	[1]	(122,089,000)	[1]	(52,278,000)	30,326,000
Other Comprehensive Income Before Reclassifications					229,288,000		(166,824,000)
Reclassified from Accumulated Oher Comprehensive Income					(728,000)		(431,000)
Other Comprehensive Income (Loss), before Tax					228,560,000		(167,255,000)
Other Comprehensive Income (Loss), Tax					(57,139,000)		41,813,000
Other comprehensive income (loss), net of tax					171,421,000		(125,442,000)
Reclassification Where Impairment Was Not Previously Recognized					(35,000)		(12,000)
Pension Loss [Member]
Accumulated other comprehensive income (loss)	(21,941,000)	[2]	(22,591,000)	[2]	(21,941,000)	[2]	(22,591,000)	[2]	(23,107,000)	(19,629,000)
Other Comprehensive Income Before Reclassifications					0		0
Reclassified from Accumulated Oher Comprehensive Income					1,554,000		1,573,000
Other Comprehensive Income (Loss), before Tax					1,554,000		1,573,000
Other Comprehensive Income (Loss), Tax					(388,000)		(393,000)
Other comprehensive income (loss), net of tax					1,166,000		1,180,000
Reclassification Where Impairment Was Not Previously Recognized					0		0
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated other comprehensive income (loss)	$ 43,542,000	[2]	$ (1,029,000)	[2]	43,542,000	[2]	(1,029,000)	[2]	$ 6,855,000	$ 0
Other Comprehensive Income Before Reclassifications					46,165,000		(1,625,000)
Reclassified from Accumulated Oher Comprehensive Income					2,751,000		253,000
Other Comprehensive Income (Loss), before Tax					48,916,000		(1,372,000)
Other Comprehensive Income (Loss), Tax					(12,229,000)		343,000
Other comprehensive income (loss), net of tax					36,687,000		(1,029,000)
Reclassification Where Impairment Was Not Previously Recognized					$ 0		0
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							2,932,000
Accounting Standards Update 2018-02 [Member] | Unrealized Gain Loss on Securities OTTI [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							715,000
Accounting Standards Update 2018-02 [Member] | Unrealized Gain Loss on Securities Other [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							6,359,000
Accounting Standards Update 2018-02 [Member] | Pension Loss [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							(4,142,000)
Accounting Standards Update 2018-02 [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							0
Accounting Standards Update 2016-01 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							(33,320,000)
Accounting Standards Update 2016-01 [Member] | Unrealized Gain Loss on Securities OTTI [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							0
Accounting Standards Update 2016-01 [Member] | Unrealized Gain Loss on Securities Other [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							(33,320,000)
Accounting Standards Update 2016-01 [Member] | Pension Loss [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							0
Accounting Standards Update 2016-01 [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification							$ 0

[1] The pre-tax amounts reclassified from accumulated other comprehensive income to current earnings are included in "investment securities gains, net" in the consolidated statements of income.

[2] The pre-tax amounts reclassified from accumulated other comprehensive income to current earnings are included in "interest and fees on loans" in the consolidated statements of income.