Fair Values of Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	$ 1,041,380	$ 831,223
Other investments	11,700	10,600
Other Investments	12,838	12,227
Loans Held for Sale	18,583	33,436
Premises and Equipment		442
Other Assets	41,786	60,981
Total Assets	(1,114,587)	(938,309)
Other Liabilities	34,263	61,308
Total Liabilities	34,263	61,308
US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	5,662	7,230
US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	362,290	191,180
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	629,974	496,033
Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	981	100,998
Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	9,524	11,397
Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	32,949	24,385
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Other investments		0
Other Investments	0
Loans Held for Sale	0	0
Premises and Equipment		0
Other Assets	0	0
Total Assets	0	0
Other Liabilities	0	0
Total Liabilities	0	0
Level 1 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 1 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 1 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 1 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 1 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 1 [Member] | Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	1,041,380	831,223
Other Investments	11,668	10,557
Loans Held for Sale	18,583	33,436
Premises and Equipment		442
Other Assets	26,805	54,362
Total Assets	(1,098,436)	(930,020)
Other Liabilities	34,263	61,308
Total Liabilities	34,263	61,308
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	5,662	7,230
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	362,290	191,180
Fair Value, Inputs, Level 2 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	629,974	496,033
Fair Value, Inputs, Level 2 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	981	100,998
Fair Value, Inputs, Level 2 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	9,524	11,397
Fair Value, Inputs, Level 2 [Member] | Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	32,949	24,385
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Loans Held for Sale	0	0
Premises and Equipment		0
Other Assets	14,981	6,619
Total Assets	(16,151)	(8,289)
Other Liabilities	0	0
Total Liabilities	0	0
Level 3 [Member] | Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Investments	1,170	1,670
Level 3 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 3 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Commercial [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 3 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 3 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 3 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	0	0
Level 3 [Member] | Corporate Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated Fair Value of Available for Sale	$ 0	$ 0