Fair Values of Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2023		Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	$ 48,979		$ 26,414
Loans Held for Sale	33,127		11,869
Other Assets	92,231	[1]	68,429	[2]
Total Assets	991,940		869,373
Other Liabilities	99,441	[1]	89,298	[2]
Total Liabilities	99,441		89,298
Investments, Fair Value Disclosure	817,603		762,661
Limited Partnership Investment [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Assets	26,397		17,691
US Government Agencies Residential Mortgage-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	3,426		3,983
US Government Agency Debt Securities Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	364,811		271,416
Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	411,258		448,989
Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	887		882
Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	7,753		8,187
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	29,468		29,204
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	0		0
Loans Held for Sale	0		0
Other Assets	0	[1]	0	[2]
Total Assets	0		0
Other Liabilities	0	[1]	0	[2]
Total Liabilities	0		0
Investments, Fair Value Disclosure	0		0
Level 1 [Member] | US Government Agencies Residential Mortgage-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 1 [Member] | US Government Agency Debt Securities Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 1 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 1 [Member] | Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 1 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	42,797		25,244
Loans Held for Sale	33,127		11,869
Other Assets	65,834	[1]	50,738	[2]
Total Assets	959,361		850,512
Other Liabilities	99,441	[1]	89,298	[2]
Total Liabilities	99,441		89,298
Investments, Fair Value Disclosure	817,603		762,661
Level 2 [Member] | US Government Agencies Residential Mortgage-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	3,426		3,983
Level 2 [Member] | US Government Agency Debt Securities Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	364,811		271,416
Level 2 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	411,258		448,989
Level 2 [Member] | Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	887		882
Level 2 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	7,753		8,187
Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	29,468		29,204
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments	6,182		1,170
Loans Held for Sale	0		0
Other Assets	26,397	[1]	17,691	[2]
Total Assets	32,579		18,861
Other Liabilities	0	[1]	0	[2]
Total Liabilities	0		0
Investments, Fair Value Disclosure	0		0
Level 3 [Member] | US Government Agencies Residential Mortgage-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 3 [Member] | US Government Agency Debt Securities Commercial [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 3 [Member] | Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 3 [Member] | Obligations of U.S. Government-Sponsored Enterprises - Other Government-Sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 3 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0		0
Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	$ 0		$ 0

[1] Hedging and non-hedging interest rate derivatives and limited partnership investments

[2] on-hedging interest rate derivatives and limited partnership investments