Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), before Tax		$ (24,499)		$ (24,499)			$ (104,352)
Deferred tax expense (benefit)		(9,715)		(9,715)			(39,912)
Accumulated other comprehensive income (loss), net of tax		(14,784)	$ (34,876)	(14,784)	$ (34,876)	$ (15,027)	(64,440)	$ (51,159)	$ (52,981)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(965)	1,632	7,617	1,327
Amortization of actuarial losses and prior service cost		(1,714)	(2,863)	(5,144)	(8,531)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax		1,768	2,916	5,302	8,689
Unrealized Gains on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), before Tax		48,618		48,618			(24,504)
Deferred tax expense (benefit)		18,288		18,288			(9,379)
Accumulated other comprehensive income (loss), net of tax	[1]	30,330	16,628	30,330	16,628	31,213	(15,125)	2,604	5,098
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	161	3,470	10,926	6,692
Funded Status of Defined Benefit Plan
Accumulated Other Comprehensive Income (Loss), before Tax		(73,117)		(73,117)			(78,419)
Deferred tax expense (benefit)		(28,003)		(28,003)			(29,996)
Accumulated other comprehensive income (loss), net of tax	[1]	(45,114)	(50,050)	(45,114)	(50,050)	(46,240)	(48,423)	(51,888)	(55,415)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(1,126)	(1,838)	(3,309)	(5,365)
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), before Tax		0		0			(1,429)
Deferred tax expense (benefit)		0		0			(537)
Accumulated other comprehensive income (loss), net of tax	[1]	0	(1,454)	0	(1,454)	$ 0	$ (892)	$ (1,875)	$ (2,664)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	$ 0	$ 0	$ 0	$ 0

[1] All amounts are net of tax.