Comprehensive Income (Schedule Of Amounts Recognized In Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Net income	$ 17,016	$ 10,523	$ 33,449	$ 20,592
Unrealized holding gains arising during the period	22,769	25,962	31,292	42,070
Reclassification for securities transferred to held-to-maturity	0	(9,371)	0	(9,371)
Reclassification adjustment for securities gains realized in income	(666)	(6,008)	(2,165)	(9,511)
Other-than-temporary-impairment on available-for-sale debt securities recorded in other comprehensive income	(1,233)	0	(1,233)	(1,133)
Other-than-temporary-impairment on available-for-sale debt securities associated with credit loss realized in income	200	2,764	499	3,269
Income tax effect	(8,371)	(5,379)	(11,053)	(10,320)
Changes In Securities Held-To-Maturity [Member]
Fair value adjustment for securities transferred from available-for-sale	0	9,371	0	9,371
Amortization of fair value previously recognized into accumulated other comprehensive income	(474)	(260)	(967)	(444)
Income tax effect	190	(3,641)	387	(3,567)
Cash Flow Hedges [Member]
Net unrealized derivative gains (losses) on cash flow hedges	(291)	357	(609)	989
Reclassification adjustment on cash flow hedges	72	72	144	144
Income tax effect	88	(171)	187	(452)
Defined Benefit Pension Plans [Member]
Amortization of net loss recognized in income	1,080	401	1,983	802
Income tax effect	(432)	(160)	(794)	(321)
Total other comprehensive income	12,932	13,937	17,671	21,526
Other Comprehensive Income, Defined Benefit Plans, Tax, Total	$ 29,948	$ 24,460	$ 51,120	$ 42,118