Estimated Fair Value of On-Balance Sheet Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financial assets:
Securities available for sale	$ 497,606
Carrying Value
Financial assets:
Cash and due from banks	37,349	37,911
Interest-bearing deposits	123,408	61,942
Securities available for sale	497,606	517,213
Loans and leases, net	1,127,006	1,234,893
Accrued interest receivable	5,703	6,227
Financial liabilities:
Deposits	1,780,495	1,811,673
Short-term borrowings	20,000	20,000
FHLB advances and long-term debt	45,326	70,539
Accrued interest payable	2,857	2,916
Estimated Fair Value
Financial assets:
Cash and due from banks	37,349	37,911
Interest-bearing deposits	123,408	61,942
Securities available for sale	497,606	517,213
Loans and leases, net	1,108,278	1,213,983
Accrued interest receivable	5,703	6,227
Financial liabilities:
Deposits	1,783,403	1,815,613
Short-term borrowings	20,433	20,676
FHLB advances and long-term debt	29,005	54,096
Accrued interest payable	2,857	2,916
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and due from banks	37,349
Interest-bearing deposits	123,408
Securities available for sale	0
Loans and leases, net	0
Accrued interest receivable	0
Financial liabilities:
Deposits	0
Short-term borrowings	0
FHLB advances and long-term debt	0
Accrued interest payable	0
Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and due from banks	0
Interest-bearing deposits	0
Securities available for sale	497,606
Loans and leases, net	0
Accrued interest receivable	0
Financial liabilities:
Deposits	0
Short-term borrowings	0
FHLB advances and long-term debt	0
Accrued interest payable	0
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and due from banks	0
Interest-bearing deposits	0
Securities available for sale	0
Loans and leases, net	1,108,278
Accrued interest receivable	5,703
Financial liabilities:
Deposits	1,783,403
Short-term borrowings	20,433
FHLB advances and long-term debt	29,005
Accrued interest payable	$ 2,857