Fair Value Measurement - Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurements on Recurring Basis - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 2,373,143	$ 2,220,216
Marketable equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	2,801	2,938
Obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	1,690,744	1,257,389
Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	267,195	192,244
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	7,616	6,756
Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	397,352	751,549
Loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	1,030	3,466
Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,405	5,874
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	2,801	2,938
Level 1 | Marketable equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	2,801	2,938
Level 1 | Obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 1 | Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 1 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 1 | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 1 | Loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 1 | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	2,363,937	2,211,404
Level 2 | Marketable equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 2 | Obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	1,690,744	1,257,389
Level 2 | Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	267,195	192,244
Level 2 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	7,616	6,756
Level 2 | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	397,352	751,549
Level 2 | Loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	1,030	3,466
Level 2 | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,405	5,874
Level 3 | Marketable equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 3 | Obligations of U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 3 | Obligations of states and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 3 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 3 | Asset backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 3 | Loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value		0
Level 3 | Mortgage servicing rights
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 6,405	$ 5,874