Accumulated Other Comprehensive Income (Loss) (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), before Tax		$ (38,596)		$ (104,352)
Deferred tax expense (benefit)		(14,772)		(39,912)
Accumulated other comprehensive income (loss), net of tax		(23,824)	$ (35,411)	(64,440)	$ (52,981)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		1,838	1,386
Amortization of actuarial losses and prior service cost		1,652	2,886
Unrealized Gains on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss), before Tax		38,900		(24,504)
Deferred tax expense (benefit)		14,866		(9,379)
Accumulated other comprehensive income (loss), net of tax	[1]	24,034	20,551	(15,125)	5,098
Income taxes		(1,770)	(1,977)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	2,858	3,149
Funded Status of Defined Benefit Plan
Accumulated Other Comprehensive Income (Loss), before Tax		(76,767)		(78,419)
Deferred tax expense (benefit)		(29,364)		(29,996)
Accumulated other comprehensive income (loss), net of tax	[1]	(47,403)	(53,652)	(48,423)	(55,415)
Income taxes		632	1,123
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(1,020)	(1,763)
Employee Benefits, prior service costs		(52)	(53)
Amortization of actuarial losses and prior service cost		(1,600)	(2,833)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax		(1,652)	(2,886)
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), before Tax		(729)		(1,429)
Deferred tax expense (benefit)		(274)		(537)
Accumulated other comprehensive income (loss), net of tax	[1]	(455)	(2,310)	$ (892)	$ (2,664)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	$ 0	$ 0

[1] All amounts are net of tax.