Carrying Amounts and Estimated Fair Value for Financial Instrument Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Readily Available Market Prices (Level 1)
Financial assets:
Cash and due from banks	$ 48,933
FHLB and Federal Reserve Bank stock	21,034
Trading account assets	2,259
Financial liabilities:
Deposits	1,153,974
Other borrowed funds	204,492
Interest payable	905
Observable Market Data (Level 2)
Financial assets:
Securities available for sale	730,630
Mortgage servicing rights	813
Interest receivable	6,373
Financial liabilities:
Deposits	544,257
FHLB advances	177,668
Commercial repurchase agreements	69,588
Junior subordinated debentures	43,794
Interest rate swap agreements	12,718
Company Determined Fair Value (Level 3)
Financial assets:
Loans receivable, net of allowance	1,543,450
Carrying Amount
Financial assets:
Cash and due from banks	48,933	39,325
Securities available for sale	730,630	590,036
FHLB and Federal Reserve Bank stock	21,034	21,962
Trading account assets	2,259	2,244
Loans held for sale		6,061
Loans receivable, net of allowance	1,517,749	1,491,017
Mortgage servicing rights	561	768
Interest receivable	6,373	6,431
Financial liabilities:
Deposits	1,689,319	1,591,366
FHLB advances	171,519	136,860
Commercial repurchase agreements	66,199	71,243
Other borrowed funds	204,492	204,413
Junior subordinated debentures	43,794	43,717
Interest payable	905	1,093
Interest rate swap agreements	12,718	11,387
Fair Value
Financial assets:
Cash and due from banks	48,933	39,325
Securities available for sale	730,630	590,036
FHLB and Federal Reserve Bank stock	21,034	21,962
Trading account assets	2,259	2,244
Loans held for sale		6,268
Loans receivable, net of allowance	1,543,450	1,510,277
Mortgage servicing rights	813	1,138
Interest receivable	6,373	6,431
Financial liabilities:
Deposits	1,698,231	1,600,222
FHLB advances	177,668	143,642
Commercial repurchase agreements	69,588	75,342
Other borrowed funds	204,492	204,413
Junior subordinated debentures	43,794	43,717
Interest payable	905	1,093
Interest rate swap agreements	$ 12,718	$ 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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