Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($)		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated other comprehensive income (loss)		$ 253,136,000	$ 11,981,000	$ 110,444,000	$ (64,669,000)
Other Comprehensive Income Before Reclassifications		189,559,000	101,696,000
Reclassified from Accumulated Oher Comprehensive Income		696,000	502,000
Other Comprehensive Income (Loss), before Tax		190,255,000	102,198,000
Other Comprehensive Income (Loss), Tax		(47,563,000)	(25,548,000)
Other comprehensive income (loss), net of tax		142,692,000	76,650,000
Unrealized Gain Loss on Securities OTTI [Member]
Accumulated other comprehensive income (loss)	[1]	0	3,902,000	3,264,000	3,861,000
Other Comprehensive Income Before Reclassifications	[1]	0	55,000
Reclassified from Accumulated Oher Comprehensive Income	[1]	0	0
Other Comprehensive Income (Loss), before Tax	[1]	0	55,000
Other Comprehensive Income (Loss), Tax	[1]	0	(14,000)
Other comprehensive income (loss), net of tax	[1]	0	41,000
Unrealized Gain Loss on Securities Other [Member]
Accumulated other comprehensive income (loss)	[1]	180,745,000	21,163,000	98,809,000	(52,278,000)
Other Comprehensive Income Before Reclassifications	[1]	104,942,000	98,614,000
Reclassified from Accumulated Oher Comprehensive Income	[1]	(46,000)	(694,000)
Other Comprehensive Income (Loss), before Tax	[1]	104,896,000	97,920,000
Other Comprehensive Income (Loss), Tax	[1]	(26,224,000)	(24,479,000)
Other comprehensive income (loss), net of tax	[1]	78,672,000	73,441,000
Pension Loss [Member]
Accumulated other comprehensive income (loss)		(21,584,000)	(22,718,000)	(21,940,000)	(23,107,000)
Other Comprehensive Income Before Reclassifications		0	0
Reclassified from Accumulated Oher Comprehensive Income		474,000	518,000
Other Comprehensive Income (Loss), before Tax		474,000	518,000
Other Comprehensive Income (Loss), Tax		(118,000)	(129,000)
Other comprehensive income (loss), net of tax		356,000	389,000
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated other comprehensive income (loss)	[2]	93,975,000	9,634,000	$ 30,311,000	$ 6,855,000
Other Comprehensive Income Before Reclassifications	[2]	84,617,000	3,027,000
Reclassified from Accumulated Oher Comprehensive Income	[2]	268,000	678,000
Other Comprehensive Income (Loss), before Tax	[2]	84,885,000	3,705,000
Other Comprehensive Income (Loss), Tax	[2]	(21,221,000)	(926,000)
Other comprehensive income (loss), net of tax	[2]	63,664,000	$ 2,779,000
Accounting Standards Update 2016-13
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		0
Accounting Standards Update 2016-13 | Unrealized Gain Loss on Securities OTTI [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	[1]	(3,264,000)
Accounting Standards Update 2016-13 | Unrealized Gain Loss on Securities Other [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	[1]	3,264,000
Accounting Standards Update 2016-13 | Pension Loss [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification		0
Accounting Standards Update 2016-13 | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	[2]	$ 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.