Summary of Significant Accounting Policies - Additional Information (Detail)	2 Months Ended	3 Months Ended		7 Months Ended	9 Months Ended
	Jul. 31, 2022 $ / shares shares	Sep. 30, 2023 USD ($) shares	Sep. 30, 2022 USD ($) shares	Jul. 27, 2021 shares	Sep. 30, 2023 USD ($) Location $ / shares shares	Sep. 30, 2022 USD ($) shares	Dec. 31, 2022 USD ($)
Equity, Class of Treasury Stock [Line Items]
Number of locations | Location					80
Minimum number of shares that company is required to repurchase | shares				0
Amount of allowance for credit loss		$ 0	$ 0		$ 0	$ 0	$ 0
Shares repurchased and retired average price | $ / shares	$ 38.61				$ 26.99
Minimum number of days to consider the loans as non-accrual					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)	$ (632,421,000)		$ (639,934,000)	$ (632,421,000)	(535,228,000)
First financial antidilutive securities excluded from eps computation | shares		864,000	346,000		478,000	272,000
Shares repurchased under stock repurchase authorization, shares | shares	244,559				101,337
Deferred Tax Assets		$ 173,032,000,000	$ 168,398,000,000		$ 173,032,000,000	$ 168,398,000,000	145,511,000,000
Commitments to Extend Credit [Member]
Equity, Class of Treasury Stock [Line Items]
Reserve for unfunded commitments		7,903,000	10,879,000		7,903,000	10,879,000	12,323,000
Held-to-maturity Securities [Member]
Equity, Class of Treasury Stock [Line Items]
Securities held to maturity		$ 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