Carrying Amounts and Estimated Fair Value for Financial Instrument Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Readily Available Market Prices (Level 1)
Financial assets:
Cash and due from banks	$ 40,478
FHLB and Federal Reserve Bank stock	21,034
Trading account assets	2,184
Financial liabilities:
Deposits	1,070,414
Other borrowed funds	166,222
Interest payable	928
Observable Market Data (Level 2)
Financial assets:
Securities available for sale	677,262
Mortgage servicing rights	976
Interest receivable	6,530
Financial liabilities:
Deposits	539,735
FHLB advances	258,173
Commercial repurchase agreements	69,850
Junior subordinated debentures	43,768
Interest rate swap agreements	12,820
Company Determined Fair Value (Level 3)
Financial assets:
Loans receivable, net of allowance	1,534,591
Carrying Amount
Financial assets:
Cash and due from banks	40,478	39,325
Securities available for sale	677,262	590,036
FHLB and Federal Reserve Bank stock	21,034	21,962
Trading account assets	2,184	2,244
Loans held for sale		6,061
Loans receivable, net of allowance	1,513,202	1,491,017
Mortgage servicing rights	688	768
Interest receivable	6,530	6,431
Financial liabilities:
Deposits	1,601,861	1,591,366
FHLB advances	251,613	136,860
Commercial repurchase agreements	66,210	71,243
Other borrowed funds	166,222	204,413
Junior subordinated debentures	43,768	43,717
Interest payable	928	1,093
Interest rate swap agreements	12,820	11,387
Fair Value
Financial assets:
Cash and due from banks	40,478	39,325
Securities available for sale	677,262	590,036
FHLB and Federal Reserve Bank stock	21,034	21,962
Trading account assets	2,184	2,244
Loans held for sale		6,268
Loans receivable, net of allowance	1,534,591	1,510,277
Mortgage servicing rights	976	1,138
Interest receivable	6,530	6,431
Financial liabilities:
Deposits	1,610,149	1,600,222
FHLB advances	258,173	143,642
Commercial repurchase agreements	69,850	75,342
Other borrowed funds	166,222	204,413
Junior subordinated debentures	43,768	43,717
Interest payable	928	1,093
Interest rate swap agreements	$ 12,820	$ 11,387

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Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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