Fair Value of Financial Measurements - Schedule of Fair Value of Measurements (Detail) - USD ($) $ in Thousands	Jun. 30, 2022		Dec. 31, 2021
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	$ 635,458		$ 669,354
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0		364
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	635,458		668,990
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0		0
U.S. government and agency securities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	99,460	[1]	73,825	[2]
U.S. government and agency securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0		364
U.S. government and agency securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	99,460		73,461
U.S. government and agency securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0		0
States, Municipalities and Political Subdivisions [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	95,821		105,699
States, Municipalities and Political Subdivisions [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0		0
States, Municipalities and Political Subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	95,821		105,699
States, Municipalities and Political Subdivisions [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0		0
Special Revenue [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	271,692		288,569
Special Revenue [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0
Special Revenue [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	271,692		288,569
Special Revenue [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0		0
Hybrid Securities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale			99
Hybrid Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale
Hybrid Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale			99
Hybrid Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale			0
Industrial and Miscellaneous [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	168,485		201,162
Industrial and Miscellaneous [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	0
Industrial and Miscellaneous [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	168,485		201,162
Industrial and Miscellaneous [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt securities, available-for-sale	$ 0		$ 0

[1] Includes securities at June 30, 2022 with a carrying amount of $28.3 million that were pledged as collateral for the advance agreement entered into with a financial institution in 2018. The Company is permitted to withdraw or exchange any portion of the pledged collateral over the minimum requirement at any time.

[2] Includes securities at December 31, 2021 with a carrying amount of $22.5 million that were pledged as collateral for the advance agreement entered into with a financial institution in 2018. The Company is permitted to withdraw or exchange any portion of the pledged collateral over the minimum requirement at any time.