Loans - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans net of unearned discount and deferred loan fees	$ 6,100,000		$ 5,600,000
Transfer of certain non-performing loans to loans held for sale	35,600,000
Non-covered loans	11,613,664,000		11,471,447,000
Sales of loans	0	0
Non-interest income, increase (decrease)	76,000	3,200,000
Reimbursable portion of valuation write-downs on certain covered OREO properties	1,256,000	0
Combined loan-to-value ratio home equity loan	75.00%
TDRs not reported as non-accrual loans	114,700,000		107,000,000
Non-performing TDRs	24,100,000		48,400,000
Specific reserves for loan losses	2,100,000	1,600,000
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
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unsecured loans	328,600,000		314,600,000
Commercial and Industrial [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Impaired loans	250,000
PCI Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding contractual principal balances	212,100,000		227,200,000
Non-covered loans	736,000,000		796,100,000
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-covered loans	1,624,846,000		1,565,492,000
Unsecured loans	23,800,000		21,400,000
Credit Card [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unsecured loans	$ 7,600,000		$ 8,300,000