Comprehensive Income (Schedule Of Amounts Recognized In Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Net income	$ 16,797	$ 11,896	$ 50,246	$ 32,488
Unrealized holding gains arising during the period	16,032	26,709	47,324	68,779
Reclassification for securities transferred to held-to-maturity	0	0	0	(9,371)
Reclassification adjustment for securities gains realized in income	(2,861)	(3,281)	(5,026)	(12,792)
Other-than-temporary-impairment on available-for-sale debt securities recorded in other comprehensive income	(140)	0	(1,373)	(1,133)
Other-than-temporary-impairment on available-for-sale debt securities associated with credit loss realized in income	0	39	499	3,308
Income tax effect	(5,149)	(9,176)	(16,202)	(19,496)
Changes In Securities Held-To-Maturity [Member]
Fair value adjustment for securities transferred from available-for-sale	0	0	0	9,371
Amortization of fair value previously recognized into accumulated other comprehensive income	(337)	(416)	(1,304)	(860)
Income tax effect	134	166	521	(3,401)
Cash Flow Hedges [Member]
Net unrealized derivative gains (losses) on cash flow hedges	(412)	201	(1,021)	1,190
Reclassification adjustment on cash flow hedges	72	72	216	216
Income tax effect	137	(109)	324	(561)
Defined Benefit Pension Plans [Member]
Amortization of net loss recognized in income	1,154	750	3,137	1,552
Income tax effect	(461)	(299)	(1,255)	(620)
Total other comprehensive income	8,169	14,656	25,840	36,182
Other Comprehensive Income, Defined Benefit Plans, Tax, Total	$ 24,966	$ 26,552	$ 76,086	$ 68,670