Loans and Allowance for Credit Losses - Outstanding Balances of Loan (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ (8,656,945)	$ (7,642,143)
Commercial, financial, agricultural and other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(1,471,079)	(1,211,706)
Commercial, financial, agricultural and other [Member] | Time and Demand Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(1,254,315)	(1,023,824)
Commercial, financial, agricultural and other [Member] | Commercial Credit Cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(13,706)	(13,920)
Commercial, financial, agricultural and other [Member] | Equipment Finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(109,221)	(79,674)
Commercial, financial, agricultural and other [Member] | Time and Demand Loans Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(93,837)	(94,288)
Real estate construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(541,902)	(513,101)
Real estate construction [Member] | Construction Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(422,831)	(395,439)
Real estate construction [Member] | Construction Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(119,071)	(117,662)
Residential real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(2,323,867)	(2,194,669)
Residential real estate [Member] | Senior Lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(1,660,433)	(1,547,192)
Residential real estate [Member] | Junior Lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(663,434)	(647,477)
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(2,991,930)	(2,425,012)
Commercial Real Estate [Member] | Multifamily
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(484,193)	(431,151)
Commercial Real Estate [Member] | Nonowner Occupied Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(1,817,453)	(1,510,347)
Commercial Real Estate [Member] | Owner Occupied Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(690,284)	(483,514)
Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(1,328,167)	(1,297,655)
Loans to individuals [Member] | Automobiles
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(1,244,874)	(1,210,451)
Loans to individuals [Member] | Consumer Credit Cards
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	(9,886)	(10,657)
Loans to individuals [Member] | Other Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ (73,407)	$ (76,547)