Fair Value Measurements - Estimated Fair Values of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024
FINANCIAL ASSETS
Federal funds sold, Carrying Amount	$ 0	$ 715
Debt securities held for investment, Carrying Amount	561	837
Loans, net of allowance for credit losses, Carrying Amount	8,017,500	7,925,613
Debt securities held for investment, Fair Value	561	837
Loans held for sale, Fair Value	10,009	8,073
FINANCIAL LIABILITIES
Deposits, Carrying Amount	12,056,192	11,718,546	$ 11,015,602
Short-term borrowings, Carrying Amount	5,860	0
Subordinated debt, Carrying Amount	86,185	86,157
OFF-BALANCE SHEET FINANCIAL INSTRUMENTS
Loan commitments, Fair Value	4,148	4,313
Letters of credit, Fair Value	667	769
Level 2 Inputs [Member]
FINANCIAL ASSETS
Cash and cash equivalents, Carrying Amount	3,997,350	3,553,772
Federal funds sold, Carrying Amount	0	715
Debt securities held for investment, Carrying Amount	560	835
Loans held for sale, Carrying Amount	10,009	8,073
Cash and cash equivalents, Fair Value	3,997,350	3,553,772
Federal funds sold, Fair Value	0	715
Debt securities held for investment, Fair Value	560	835
Loans held for sale, Fair Value	10,009	8,073
FINANCIAL LIABILITIES
Deposits, Carrying Amount	12,056,192	11,718,546
Short-term borrowings, Carrying Amount	5,860
Subordinated debt, Carrying Amount	86,185	86,157
Deposits, Fair Value	11,347,850	10,966,958
Short-term borrowings, Fair Value	5,860
Subordinated debt, Fair Value	80,644	77,998
Level 3 Inputs [Member]
FINANCIAL ASSETS
Debt securities held for investment, Carrying Amount	1	2
Loans, net of allowance for credit losses, Carrying Amount	8,017,500	7,925,613
Debt securities held for investment, Fair Value	1	2
Loans, net of allowance for credit losses, Fair Value	$ 8,845,583	$ 8,643,418