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Capital Ratios (Details) (USD $)	1 Months Ended		9 Months Ended
	Mar. 31, 2009 year	Mar. 31, 2005 year	Sep. 30, 2011	Dec. 31, 2010	Dec. 31, 2009
Capital Ratios
Tier 1 capital to average total asset (leverage) ratio (as a percent)			12.15%	11.58%
Risk-weighted Tier 1 capital ratio (as a percent)			22.09%	19.47%
Risk-weighted total capital ratio (as a percent)			23.34%	20.72%
Identified intangibles and goodwill			$ 295,972,000
Percentage of capital securities issued by trust qualifying as Tier I capital, maximum (as a percent)			25.00%
Capital securities issued by the trust, qualifying as Tier I capital			190,726,000	201,117,000
Length of transition period under final rule of Federal Reserve Board (in years)		5
Percentage of trust preferred securities and certain other capital elements to Tier 1 capital, maximum (as a percent)			25.00%
Percentage of trust preferred securities to tier 1 capital for bank holding companies with significant international operations, maximum limit expected (as a percent)			15.00%
Percentage of convertible preferred securities to Tier 1 capital elements related to bank holding companies with significant international operations, maximum (as a percent)			25.00%
Extended transition period under the final rule of the Federal Reserve Board (in years)	2
Consolidated assets required for the application of Collins amendment, minimum					$ 15,000,000,000

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The number of years specified as the extended transition period under the final rule of the Federal Reserve Board.

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The length of the transition period under final rule of Federal Reserve Board limiting the 25% Tier I capital to trust preferred securities and certain other elements.

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Maximum percentage of qualifying mandatory convertible preferred securities to Tier 1 capital elements related to bank holding companies with significant international operations.

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Maximum percentage of the aggregate amount of trust preferred securities and certain other capital elements to Tier 1 capital elements, net of goodwill, less any associated deferred tax liability.

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Minimum amounts of consolidated assets required for the application of Collins amendment as per Dodd-Frank Wall Street Reform and Consumer Protection Act.

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For bank holding companies with significant international operations, the expected maximum percentage of trust preferred securities to tier I capital.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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