Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated other comprehensive income (loss)		$ 349,261,000	$ 108,898,000	$ 349,261,000	$ 108,898,000	$ 110,444,000	$ (64,669,000)
Other Comprehensive Income Before Reclassifications				322,653,000	229,303,000
Reclassified from Accumulated Oher Comprehensive Income				(4,231,000)	2,118,000
Other Comprehensive Income (Loss), before Tax				318,422,000	231,421,000
Other Comprehensive Income (Loss), Tax				(79,605,000)	(57,854,000)
Other comprehensive income (loss), net of tax		96,125,000	96,917,000	238,817,000	173,567,000
Reclassification Where Impairment Was Not Previously Recognized					0
Cumulative Effect, Period of Adoption, Adjustment
Accumulated other comprehensive income (loss)						0
Cumulative Effect, Period of Adoption, Adjusted Balance
Accumulated other comprehensive income (loss)						110,444,000
Unrealized Gain Loss on Securities OTTI [Member]
Accumulated other comprehensive income (loss)	[1]	0	3,709,000	0	3,709,000	3,264,000	3,861,000
Other Comprehensive Income Before Reclassifications	[1]			0	(312,000)
Reclassified from Accumulated Oher Comprehensive Income	[1]			0	63,000
Other Comprehensive Income (Loss), before Tax	[1]			0	(249,000)
Other Comprehensive Income (Loss), Tax	[1]			0	62,000
Other comprehensive income (loss), net of tax	[1]			0	(187,000)
Reclassification Where Impairment Was Not Previously Recognized					35,000
Unrealized Gain Loss on Securities OTTI [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated other comprehensive income (loss)	[1]					(3,264,000)
Unrealized Gain Loss on Securities OTTI [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance
Accumulated other comprehensive income (loss)						0
Unrealized Gain Loss on Securities Other [Member]
Accumulated other comprehensive income (loss)	[1]	267,207,000	98,078,000	267,207,000	98,078,000	98,809,000	(52,278,000)
Other Comprehensive Income Before Reclassifications	[1]			223,470,000	201,210,000
Reclassified from Accumulated Oher Comprehensive Income	[1]			(3,292,000)	(690,000)
Other Comprehensive Income (Loss), before Tax	[1]			220,178,000	200,520,000
Other Comprehensive Income (Loss), Tax	[1]			(55,044,000)	(50,129,000)
Other comprehensive income (loss), net of tax	[1]			165,134,000	150,391,000
Reclassification Where Impairment Was Not Previously Recognized					(35,000)
Unrealized Gain Loss on Securities Other [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated other comprehensive income (loss)	[1]					3,264,000
Unrealized Gain Loss on Securities Other [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance
Accumulated other comprehensive income (loss)						102,073,000
Pension Loss [Member]
Accumulated other comprehensive income (loss)		(21,229,000)	(22,330,000)	(21,229,000)	(22,330,000)	(21,940,000)	(23,107,000)
Other Comprehensive Income Before Reclassifications				0	0
Reclassified from Accumulated Oher Comprehensive Income				948,000	1,036,000
Other Comprehensive Income (Loss), before Tax				948,000	1,036,000
Other Comprehensive Income (Loss), Tax				(237,000)	(259,000)
Other comprehensive income (loss), net of tax				711,000	777,000
Reclassification Where Impairment Was Not Previously Recognized					0
Pension Loss [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated other comprehensive income (loss)						0
Pension Loss [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance
Accumulated other comprehensive income (loss)						(21,940,000)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated other comprehensive income (loss)	[2]	$ 103,283,000	$ 29,441,000	103,283,000	29,441,000	30,311,000	$ 6,855,000
Other Comprehensive Income Before Reclassifications	[2]			99,183,000	28,405,000
Reclassified from Accumulated Oher Comprehensive Income	[2]			(1,887,000)	1,709,000
Other Comprehensive Income (Loss), before Tax	[2]			97,296,000	30,114,000
Other Comprehensive Income (Loss), Tax	[2]			(24,324,000)	(7,528,000)
Other comprehensive income (loss), net of tax	[2]			$ 72,972,000	22,586,000
Reclassification Where Impairment Was Not Previously Recognized					$ 0
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Cumulative Effect, Period of Adoption, Adjustment
Accumulated other comprehensive income (loss)	[2]					0
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance
Accumulated other comprehensive income (loss)						$ 30,311,000

[1] The pre-tax amounts reclassified from accumulated other comprehensive income to current earnings are included in "investment securities gains (losses), 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.