Shareholders' Equity (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Other Comprehensive Income, Before Tax:
Net Unrealized Gains Arising During the Period, Before Tax	$ 40,645	$ 78,494	$ 73,528
Less: Reclassification Adjustment for Gains Realized in Net Income, Before Tax	(13,525)	(42,848)	(25,770)
Net Unrealized Gains on Investment Securities, Before Tax	27,120	35,646	47,758
Prior Service Credit from Plan Amendment During the Period, Before Tax	917
Settlement Gain Related to Defined Benefit Plan, Before Tax		(951)
Less: Amortization of Prior Service Credit Included in Net Periodic Benefit Cost, Before Tax	(322)	(213)	(213)
Net Prior Service Credit Arising During the Period, Before Tax	595
Net Actuarial Gains (Losses) Arising During the Period, Before Tax	(13,981)	(842)	8,410
Defined Benefit Plans, Net, Before Tax	(13,386)	(2,006)	8,197
Other Comprehensive Income, Before Tax	13,734	33,640	55,955
Other Comprehensive Income, Tax Effect:
Net Unrealized Gains Arising During the Period, Tax Effect	16,037	33,941	26,470
Less: Reclassification Adjustment for Gains Realized in Net Income, Tax Effect	(5,328)	(18,526)	(9,279)
Net Unrealized Gains on Investment Securities, Tax Effect	10,709	15,415	17,191
Prior Service Credit from Plan Amendment During the Period, Tax Effect	361
Settlement Gain Related to Defined Benefit Plan, Tax Effect		(343)
Less: Amortization of Prior Service Credit Included in Net Periodic Benefit Cost, Tax Effect	(127)	(84)	(77)
Net Prior Service Credit Arising During the Period, Tax Effect	234
Net Actuarial Gains (Losses) Arising During the Period, Tax Effect	(5,507)	(1,388)	3,028
Defined Benefit Plans, Net, Tax Effect	(5,273)	(1,815)	2,951
Other Comprehensive Income, Tax Effect	5,436	13,600	20,142
Other Comprehensive Income, Net of Tax:
Net Unrealized Gains Arising During the Period, Net of Tax	24,608	44,553	47,058
Less: Reclassification Adjustment for Gains Realized in Net Income, Net of Tax	(8,197)	(24,322)	(16,491)
Net Unrealized Gains on Investment Securities, Net of Tax	16,411	20,231	30,567
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Costs (Credit) Arising During Period, Net of Tax	556
Settlement Gain Related to Defined Benefit Plan, Net of Tax		(608)
Less: Amortization of Prior Service Credit Included in Net Periodic Benefit Cost, Net of Tax	(195)	(129)	(136)
Net Prior Service Credit Arising During the Period, Net of Tax	361
Net Actuarial Gains (Losses) Arising During the Period, Net of Tax	(8,474)	546	5,382
Defined Benefit Plans, Net, Net of Tax	(8,113)	(191)	5,246
Other Comprehensive Income, Net of Tax	$ 8,298	$ 20,040	$ 35,813