Basis Of Presentation And Significant Accounting Policies (Schedule Of Amounts Recognized In Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other Comprehensive Income [Line Items]
Net income	$ 22,214	$ 16,797	$ 17,016	$ 16,433	$ 5,726	$ 11,896	$ 10,523	$ 10,069	$ 72,460	$ 38,214	$ 13,737
Unrealized holding gains (losses) arising during the period									43,221	43,078	99,164
Reclassification for securities transferred to held-to-maturity									0	(9,371)	(1,791)
Reclassification adjustment for securities (gains) losses realized in income									(8,691)	(17,124)	(27,251)
Other-than-temporary-impairment on available-for-sale debt securities recorded in other comprehensive income									(1,843)	(1,133)	(43,295)
Other-than-temporary-impairment on available-for-sale debt securities associated with credit loss realized in income									1,409	3,927	24,795
Income tax effect									(13,273)	(7,876)	(18,830)
Changes In Securities Held-To-Maturity [Member]
Other Comprehensive Income [Line Items]
Fair value adjustment for securities transferred from available-for-sale									0	9,371	1,791
Amortization of fair value previously recognized into accumulated other comprehensive income									(1,535)	(1,284)	(438)
Income tax effect									613	(3,232)	(541)
Cash Flow Hedges [Member]
Other Comprehensive Income [Line Items]
Net unrealized derivative gains (losses) on cash flow hedges									(1,387)	807	821
Reclassification adjustment on cash flow hedges									216	288	288
Income tax effect									470	(436)	(442)
Defined Benefit Pension Plans [Member]
Other Comprehensive Income [Line Items]
Net loss, settlement cost and amortization of net (gain) loss recognized in income									(4,878)	3,469	(1,889)
Income tax effect									1,951	(1,387)	756
Total other comprehensive income (loss)									16,273	19,097	33,138
Comprehensive income									$ 88,733	$ 57,311	$ 46,875