Fair Value Measurement and Fair Value of Financial Instruments - Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Total securities available for sale	$ 855,746	$ 755,900
Equity securities, at fair value	14,694	16,473
Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	855,746	755,900
Equity securities, at fair value	14,694	16,473
Derivative assets	80,734	27,123
Total Assets	951,174	799,496
Liabilities:
Derivative liabilities	80,877	26,852
Total Liabilities	80,877	26,852
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	9,392	12,580
Equity securities, at fair value	0	1,735
Derivative assets	0	0
Total Assets	9,392	14,315
Liabilities:
Derivative liabilities	0	0
Total Liabilities	0	0
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	846,354	743,320
Equity securities, at fair value	14,694	14,738
Derivative assets	80,734	27,123
Total Assets	941,782	785,181
Liabilities:
Derivative liabilities	80,877	26,852
Total Liabilities	80,877	26,852
Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Equity securities, at fair value	0	0
Derivative assets	0	0
Total Assets	0	0
Liabilities:
Derivative liabilities	0	0
Total Liabilities	0	0
U.S. Treasury and U.S. government agencies
Assets:
Total securities available for sale	65,002	135,647
U.S. Treasury and U.S. government agencies \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	65,002	135,647
U.S. Treasury and U.S. government agencies \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	9,392	12,580
U.S. Treasury and U.S. government agencies \| Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	55,610	123,067
U.S. Treasury and U.S. government agencies \| Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Mortgage-backed securities \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	230,100	227,552
Mortgage-backed securities \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Mortgage-backed securities \| Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	230,100	227,552
Mortgage-backed securities \| Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Collateralized mortgage obligations \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	250,573	323,512
Collateralized mortgage obligations \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Collateralized mortgage obligations \| Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	250,573	323,512
Collateralized mortgage obligations \| Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Asset-backed securities
Assets:
Total securities available for sale	40,690
Asset-backed securities \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	40,690
Asset-backed securities \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0
Asset-backed securities \| Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	40,690
Asset-backed securities \| Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0
Obligations of states and political subdivisions
Assets:
Total securities available for sale	233,710	60,021
Obligations of states and political subdivisions \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	233,710	60,021
Obligations of states and political subdivisions \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Obligations of states and political subdivisions \| Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	233,710	60,021
Obligations of states and political subdivisions \| Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Corporate debt securities \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	35,671	9,168
Corporate debt securities \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	0	0
Corporate debt securities \| Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	35,671	9,168
Corporate debt securities \| Significant Unobservable Inputs (Level 3) \| Fair Value, Measurements, Recurring
Assets:
Total securities available for sale	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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