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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

Loans - Additional Information (Detail) (USD $)	3 Months Ended			9 Months Ended
Loans - Additional Information (Detail) (USD $)	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of purchased credit impaired loans not covered				93.00%
Average expected life of non covered PCI loans at date of acquisition				4 years
Average expected life of non covered PCI loans at reporting date				2 years 2 months
Non-covered loans net of unearned discount and deferred loan fees	$ 8,000,000			$ 8,000,000		$ 5,600,000
Non-performing loans held for sale		35,600,000
Non-covered loans	12,119,086,000			12,119,086,000		11,471,447,000
Sales of loans	0		0	0	0
Non-interest income, increase (decrease)	3,800,000		2,000,000	11,600,000	7,200,000
Reimbursable portion of valuation write-downs on certain covered OREO properties	(80,000)		0	(1,016,000)	0
Combined loan-to-value ratio home equity loan	75.00%			75.00%
TDRs not reported as non-accrual loans	107,100,000			107,100,000		107,000,000
Non-performing TDRs	22,000,000			22,000,000		48,400,000
Specific reserves for loan losses	3,800,000		5,300,000
Partial loan charge-offs related to loans modified as TDRs	861,000		1,100,000
Number of days loans placed on non-accrual status				90 days
Contributions to qualified plan	0
TDR loans full charge-offs			6,100,000
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unsecured loans	339,700,000			339,700,000		314,600,000
Commercial and Industrial [Member] \| Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans	250,000			250,000
PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding contractual principal balances	72,000,000			72,000,000		227,200,000
Non-covered loans	637,400,000			637,400,000		796,100,000
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,802,571,000			1,802,571,000		1,565,492,000
Unsecured loans	28,200,000			28,200,000		21,400,000
Credit Card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unsecured loans	$ 7,300,000			$ 7,300,000		$ 8,300,000