Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income		$ 67,061,000	$ 121,082,000	$ 67,061,000	$ 121,082,000	$ 10,975,000	$ 32,470,000
Other Comprehensive Income Before Reclassifications				95,159,000	140,915,000
Reclassified from Accumulated Oher Comprehensive Income				(4,698,000)	2,007,000
Other Comprehensive Income (Loss), before Tax				90,461,000	142,922,000
Other Comprehensive Income (Loss), Tax				(34,375,000)	(54,310,000)
Other comprehensive income (loss), net of tax		24,991,000	(13,342,000)	56,086,000	88,612,000
Reclassification Where Impairment Was Not Previously Recognized				0	0
Unrealized Gain Loss on Securities OTTI [Member]
Accumulated other comprehensive income	[1]	3,456,000	2,964,000	3,456,000	2,964,000	2,975,000	3,316,000
Other Comprehensive Income Before Reclassifications	[1]			365,000	(837,000)
Reclassified from Accumulated Oher Comprehensive Income	[1]			372,000	270,000
Other Comprehensive Income (Loss), before Tax	[1]			737,000	(567,000)
Other Comprehensive Income (Loss), Tax	[1]			(280,000)	215,000
Other comprehensive income (loss), net of tax	[1]			457,000	(352,000)
Reclassification Where Impairment Was Not Previously Recognized				24,000	0
Unrealized Gain Loss on Securities Other [Member]
Accumulated other comprehensive income	[1]	81,903,000	137,637,000	81,903,000	137,637,000	27,328,000	49,750,000
Other Comprehensive Income Before Reclassifications	[1]			94,794,000	141,752,000
Reclassified from Accumulated Oher Comprehensive Income	[1]			(6,731,000)	0
Other Comprehensive Income (Loss), before Tax	[1]			88,063,000	141,752,000
Other Comprehensive Income (Loss), Tax	[1]			(33,464,000)	(53,865,000)
Other comprehensive income (loss), net of tax	[1]			54,599,000	87,887,000
Reclassification Where Impairment Was Not Previously Recognized				(24,000)	0
Pension Loss [Member]
Accumulated other comprehensive income	[2]	$ (18,298,000)	$ (19,519,000)	(18,298,000)	(19,519,000)	$ (19,328,000)	$ (20,596,000)
Other Comprehensive Income Before Reclassifications	[2]			0	0
Reclassified from Accumulated Oher Comprehensive Income	[2]			1,661,000	1,737,000
Other Comprehensive Income (Loss), before Tax	[2]			1,661,000	1,737,000
Other Comprehensive Income (Loss), Tax	[2]			(631,000)	(660,000)
Other comprehensive income (loss), net of tax	[2]			1,030,000	1,077,000
Reclassification Where Impairment Was Not Previously Recognized				$ 0	$ 0

[1] The pre-tax amounts reclassified from accumulated other comprehensive income 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 are included in the computation of net periodic pension cost as "amortization of prior service cost" and "amortization of unrecognized net loss" (see Note 6), for inclusion in the consolidated statements of income.