Mortgage Banking Activities, Mortgage Servicing Rights (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Summary of Mortgage Servicing Rights [Abstract]
Number of residential mortgage loans serviced	95,831	99,986	95,831	99,986	96,443
Outstanding principal balance of residential mortgage loans serviced for others	$ 11,249,503	$ 11,190,802	$ 11,249,503	$ 11,190,802	$ 11,194,582
Weighted average interest rate (in hundredths)			5.29%	5.55%	5.44%
Remaining term (in months)	286 M	290 M	286 M	290 M	292 M
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	109,192	98,942	115,723	73,824	73,824
Additions, net	7,199	7,716	17,966	49,970
Change in fair value due to loan runoff	(3,621)	(4,401)	(10,555)	(16,011)
Gain on purchase of mortgage servicing rights				11,832
Change in fair value due to market changes	(24,822)	(15,924)	(35,186)	(33,282)
Ending balance	87,948	86,333	87,948	86,333	115,723
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract]
Discount rate - risk-free rate plus a market premium (in hundredths)			10.34%	10.40%	10.36%
Prepayment rate - estimated based upon loan interest rate, original term and loan type, minimum (in hundredths)			11.33%	5.20%	6.53%
Prepayment rate - estimated based upon loan interest rate, original term and loan type, maximum (in hundredths)			47.70%	56.00%	23.03%
Loan servicing costs - annually per loan based upon loan type, minimum (in dollars per loan)			55	35	35
Loan servicing costs - annually per loan based upon loan type, maximum (in dollars per loan)			105	60	60
Escrow earnings rate - indexed to rates paid on deposit accounts with comparable average life (in hundredths)			1.26%	1.51%	2.21%
Purchased [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	32,866	37,446	37,900	7,828	7,828
Additions, net	0	0	0	31,892
Change in fair value due to loan runoff	(1,034)	(2,062)	(3,585)	(4,703)
Gain on purchase of mortgage servicing rights				11,832
Change in fair value due to market changes	(10,395)	(4,022)	(12,878)	(15,487)
Ending balance	21,437	31,362	21,437	31,362
Originated [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	76,326	61,496	77,823	65,996	65,996
Additions, net	7,199	7,716	17,966	18,078
Change in fair value due to loan runoff	(2,587)	(2,339)	(6,970)	(11,308)
Gain on purchase of mortgage servicing rights				0
Change in fair value due to market changes	(14,427)	(11,902)	(22,308)	(17,795)
Ending balance	$ 66,511	$ 54,971	$ 66,511	$ 54,971

The net increase or decrease in fair value as a result of loan runoff.

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Indicates the number of mortgage loans being serviced.

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Dollar amount of principal outstanding on mortgage loans being serviced.

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The weighted average remaining term of the mortgage loans being serviced.

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The escrow earning rate used to estimate the fair value of servicing assets, based on rates paid on deposit accounts.

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The maximum cost to service a loan for the period used as a variable in estimating fair value.

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The minimum cost to service a loan for the period used as a variable in estimating fair value.

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The maximum estimated speed of prepayments of principal on financial assets which may be one of the factors applied in estimating the fair value of servicing assets.

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The minimum estimated speed of prepayments of principal on financial assets which may be one of the factors applied in estimating the fair value of servicing assets.

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The net increase or decrease in fair value as a result of changes in the assumptions or model used to calculate the fair value of servicing assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The stated interest rate on the mortgage loan receivable or the weighted average interest rate on a group of loans.

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The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

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Fair value 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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Other net Increase or Decrease in the balance in servicing assets subsequently measured at fair value. This element is for changes other than additions, disposals, changes in fair value resulting from changes in valuation inputs or changes in assumptions, or other changes in fair value.

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The discount rate used to estimate the fair value of servicing assets and servicing liabilities.

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