Borrowings - Additional Information (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2015 USD ($) Trust	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Credit available with FHLB	$ 4,467,170
Credit with FHLB used	$ 850,017
Federal Home Loan Bank advances are scheduled to mature periodically through the year	2021
Effective interest rates, minimum	0.76%	0.76%
Effective interest rates, maximum	4.19%	4.19%
Number of unconsolidated subsidiary trusts \| Trust	2
Percent of the common equity of each Trust owned by the Corporation	100.00%
Junior subordinated debt	$ 58,285	$ 58,246
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Debt Instrument [Line Items]
Percentage of TPS moving from tier 1 capital to tier 2 capital for 2015	25.00%
Junior subordinated debt	$ 57,500
Percentage of TPS moving from tier 1 capital to tier 2 capital for 2016	75.00%

Amount of advances or credit lines used from the Federal Home Loan Bank (FHLB).

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Number of unconsolidated subsidiary trusts owned by the company.

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Percentage of common equity of each unconsolidated subsidiary trust owned by the company.

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Percentage Of Trust Preferred Securities Moving From Tier One To Tier Two Capital In Next Rolling Twelve Months

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Percentage Of Trust Preferred Securities Moving From Tier One To Tier Two Capital In Rolling Year Two

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The last year of maturity for the advances from the Federal Home Loan Bank as of the Balance Sheet date.

+ References

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States the lowest interest rate applicable to any of the advances from the Federal Home Loan Bank as of the Balance Sheet date.

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States the highest interest rate applicable to any of the advances from the Federal Home Loan Bank as of the Balance Sheet date.

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Amount of maximum advances or credit lines available from the Federal Home Loan Bank (FHLB).

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Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

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