Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Dec. 31, 2009
Comprehensive Income
AOCI, Unrealized gains on available-for-sale securities	$ 58,020	$ 49,756	$ 31,962	$ 19,789
Other Comprehensive Income, Unrealized gains on available-for-sale securities	26,058	29,967
AOCI, Unrealized losses on securities for which other-than-temporary-impairment has been recognized	(29,009)	(28,173)	(28,173)	(27,501)
Other Comprehensive Income, Unrealized losses on securities for which other-than-temporary-impairment has been recognized	(836)	(672)
AOCI, Unrealized gains (losses) on held to maturity securities	4,884	5,922	5,667	812
Other Comprehensive Income, Unrealized gains (losses) on held-to-maturity securities	(783)	5,110
AOCI, Unrecognized gain (loss) on cash flow hedges	365	1,032	846	187
Other Comprehensive Income, Unrecognized gain (loss) on cash flow hedges	(481)	845
AOCI, Defined benefit pension plans	(9,689)	(12,721)	(11,571)	(13,653)
Comprehensive Income	1,882	932
Accumulated other comprehensive income (loss), net of tax	24,571	15,816	(1,269)	(20,366)
Other Comprehensive Income, Accumulated other comprehensive income (loss)	$ 25,840	$ 36,182

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