Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011
Accumulated other comprehensive income (loss), net of tax	$ (66,416)	[1]	$ (66,574)	[2]	$ (39,907)	[1]
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss)	(109,123)		(109,404)		(66,613)
Deferred tax expense (benefit)	(42,707)		(42,830)		(26,706)
Accumulated other comprehensive income (loss), net of tax	(66,416)		(66,574)		(39,907)
Unrealized gains on investment securities available for sale [Member]
Accumulated other comprehensive income (loss)	23,667		26,565		13,856
Deferred tax expense (benefit)	9,327		10,450		5,223
Accumulated other comprehensive income (loss), net of tax	14,340		16,115		8,633
Funded status of defined benefit plan [Member]
Accumulated other comprehensive income (loss)	(122,465)		(125,255)		(72,694)
Deferred tax expense (benefit)	(47,957)		(49,049)		(28,859)
Accumulated other comprehensive income (loss), net of tax	(74,508)		(76,206)		(43,835)
Unrealized loss on cash flow hedges [Member]
Accumulated other comprehensive income (loss)	(10,325)		(10,714)		(7,775)
Deferred tax expense (benefit)	(4,077)		(4,231)		(3,070)
Accumulated other comprehensive income (loss), net of tax	$ (6,248)		$ (6,483)		$ (4,705)

[1] Unaudited

[2] Derived from 2011 Annual Report on Form 10-K.