Mortgage Servicing Rights and Mortgage Servicing Activity (Details Textual) (USD $)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Servicing Assets at Fair Value [Line Items]
Residential Mortgage Loans serviced	$ 17,640,000	$ 21,317,000	$ 20,784,000	$ 18,778,000
Mortgage Servicing Rights and Mortgage Servicing Activity (Textual) [Abstract]
Unpaid principal balances from sale of residential mortgage loans	533,500,000	558,600,000
Recognized pretax gains	4,800,000	5,500,000
Related mortgage servicing rights from loans sold and receives servicing fees	481,100,000	484,000,000
Valuation Allowance for Impairment of Recognized Servicing Assets, Balance	3,500,000	0	0
Permanent impairment losses written off against valuation allowance	0	0	0
Minimum percentage adverse change in prepayment speed	10.00%
Maximum percentage adverse change in prepayment speed	25.00%
Percentage of variation in prepayment speed	10.00%
Residential Mortgages [Member]
Servicing Assets at Fair Value [Line Items]
Residential Mortgage Loans serviced	2,200,000,000	2,100,000,000
Loan servicing fees	$ 5,400,000	$ 5,100,000	$ 5,000,000

Maximum percentage adverse change in prepayment speed.

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Minimum percentage adverse change in prepayment speed.

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Percentage of variation in prepayment speed.

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All amounts that, per contract, are due to the servicer in exchange for servicing the financial asset and would no longer be received by a servicer if the beneficial owners of the serviced assets (or their trustees or agents) were to exercise their actual or potential authority under the contract to shift the servicing to another servicer. Depending on the servicing contract, those fees may include some or all of the difference between the interest rate collected on the asset being serviced and the rate to be paid to the beneficial owners of the asset.

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This is the result of the principal amount outstanding of total loans managed or securitized less securitized loans and loans that are in the process of being securitized.

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This includes the recognized portion of the total principal amount of financial assets which have been either securitized, used in an asset-backed financing arrangement, or similar transfer which are accounted for as sales and in which the transferor has continuing involvement with the assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in transferred financial assets).

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Reflects, by transferred financial asset type, the amount of sales proceeds in excess of or deficient from the sum of the carrying amounts of transferred financial assets plus transaction costs, including those transactions in which the seller/transferor has continuing involvement with the financial assets that have been transferred.

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Amortized carrying amount (balance) as of the balance sheet date of an asset representing net future revenues from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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The charge against the valuation allowance related to a servicing asset that is subsequently measured using the amortization method.

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Reflects the estimated amount of impairment as of the balance sheet date of recognized servicing assets that are being amortized in proportion to and over the period of estimated net servicing income or loss.

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