Shareholders' Equity and Stock-Based Compensation Plans Comprehensive Income (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Shareholders' Equity and Stock-Based Compensation Plans [Abstract]
Cumulative effect of FSP FAS 115-2 and FAS 124-2 adoption	$ 0		$ 0		$ (6,298,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax	12,495,000		7,458,000		(17,907,000)
Unrealized gain on securities (net of a 4.7 million, $2.2 million and 15.9 million tax effect in 2011, 2010 and 2009, respectively)	8,768,000		3,994,000		29,550,000
Non-credit related unrealized gain (loss) on other-than-temporarily impaired debt securities (net of a $129,000, $89,000 and 1.8 million tax effect in 2011, 2010 and 2009, respectively)	240,000		(166,000)		(3,385,000)
Amortization of unrealized gain on derivative financial instruments (net of a $73,000 tax effect in 2011, 2010 and 2009)	136,000	[1]	136,000	[1]	136,000	[1]
Reclassification adjustment for securities gains included in net income (net of a $1.6 million, $245,000 and $378,000 tax expense in 2011, 2010 and 2009, respectively)	(2,964,000)		(455,000)		(701,000)
(Accretion) amortization of unrecognized pension and postretirement costs (net of $26,000, $40,000 and $253,000 tax benefit in 2011, 2010 and 2009, respectively)	10,672,000		(1,454,000)		(5,592,000)
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Net of Tax	(48,000)		74,000		471,000
Other comprehensive (loss)	(4,540,000)		5,037,000		31,663,000
Accumulated Other Comprehensive Income (Loss), Net of Tax CLONE	7,955,000		12,495,000		7,458,000
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	136,000
Other Comprehensive Income (Loss), Tax [Abstract]
Cumulative effect of FSP FAS 115-2 and FAS 124-2 adoption Tax Effect	3,400,000
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	4,700,000		2,200,000		15,900,000
Other than Temporary Impairment Losses, Investments, Portion in Other Comprehensive Income (Loss), Tax, Including Portion Attributable to Noncontrolling Interest	100,000		100,000		1,800,000
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	70,000		70,000		70,000
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax	1,600,000		200,000		400,000
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Tax Effect	5,700,000		800,000		3,000,000
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Tax Effect	$ 30,000		$ 40,000		$ 300,000

[1] Amounts represent the amortization of the effective portions of losses on forward-starting interest rate swaps, designated as cash flow hedges and entered into in prior years in connection with the issuance of fixed-rate debt. The total amount recorded as a reduction to accumulated other comprehensive income upon settlement of these derivatives is being amortized to interest expense over the life of the related securities using the effective interest method. The amount of net losses in accumulated other comprehensive loss that will be reclassified into earnings during the next 12 months is expected to be approximately $136,000.