Accumulated Other Comprehensive Loss (Schedule Of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012		Dec. 31, 2011
Accumulated other comprehensive income (loss)	$ (131,280)		$ (134,923)		$ (109,123)
Deferred tax expense (benefit)	(51,375)		(52,817)		(42,707)
Accumulated other comprehensive income (loss), net of tax	(79,905)	[1]	(82,106)	[2]	(66,416)	[1]	(66,574)
Unrealized Gains on Investment Securities Available for Sale
Accumulated other comprehensive income (loss)	32,333		33,809		23,667
Deferred tax expense (benefit)	12,727		13,292		9,327
Accumulated other comprehensive income (loss), net of tax	19,606	[3]	20,517	[3]	14,340	[3]	16,115	[3]
Funded Status of Defined Benefit Plan
Accumulated other comprehensive income (loss)	(154,030)		(158,334)		(122,465)
Deferred tax expense (benefit)	(60,318)		(62,003)		(47,957)
Accumulated other comprehensive income (loss), net of tax	(93,712)	[3]	(96,331)	[3]	(74,508)	[3]	(76,206)	[3]
Unrealized Loss on Cash Flow Hedges
Accumulated other comprehensive income (loss)	(9,583)		(10,398)		(10,325)
Deferred tax expense (benefit)	(3,784)		(4,106)		(4,077)
Accumulated other comprehensive income (loss), net of tax	$ (5,799)	[3]	$ (6,292)	[3]	$ (6,248)	[3]	$ (6,483)	[3]

[1] Unaudited

[2] Derived from 2012 Annual Report on Form 10-K.

[3] All amounts are net of tax. Amounts in parentheses indicate debits.