Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	3 Months Ended		7 Months Ended	9 Months Ended
	Sep. 30, 2023 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) shares	Sep. 30, 2023 USD ($) shares	Jul. 27, 2021 shares	Sep. 30, 2024 USD ($) Location shares	Sep. 30, 2023 USD ($) shares	Dec. 31, 2023 USD ($)
Equity, Class of Treasury Stock [Line Items]
Number of locations | Location					79
Minimum number of shares that company is required to repurchase | shares				0
Amount of allowance for credit loss	$ 0	$ 0	$ 0		$ 0	$ 0	$ 0
Shares repurchased and retired average price | $ / shares	$ 26.99
Minimum number of days to consider the loans as non-accrual					90 days	90 days
Impairment recorded					$ 0	$ 0
Other identifiable intangible assets, amortized period (years)		7 years			7 years
Securities sold under agreements to repurchase maturity range (in days)					one to four days
Interest-bearing time deposits, maturity period (in days)					90 days or less
Unrealized net losses in available-for-sale securities, included in accumulated other comprehensive income	$ 639,934,000	$ 329,817,000	$ 639,934,000		$ 329,817,000	$ 639,934,000	403,298,000
First financial antidilutive securities excluded from eps computation | shares		375,000	864,000		449,000	478,000
Shares repurchased under stock repurchase authorization, shares | shares	101,337
Deferred Tax Assets	$ 173,032,000	$ 94,239,000	$ 173,032,000		$ 94,239,000	$ 173,032,000	110,800,000
Commitments to Extend Credit [Member]
Equity, Class of Treasury Stock [Line Items]
Reserve for unfunded commitments	7,903,000	8,004,000	7,903,000		8,004,000	7,903,000	7,903,000
Held-to-maturity Securities [Member]
Equity, Class of Treasury Stock [Line Items]
Securities held to maturity	$ 0	$ 0	$ 0		$ 0	$ 0	$ 0
Maximum [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, number of shares authorized to be repurchased | shares				5,000,000