Summary of Significant Accounting Policies - Additional Information (Detail)	7 Months Ended	12 Months Ended
	Jul. 27, 2021 $ / shares shares	Dec. 31, 2022 USD ($) Location $ / shares shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	Sep. 30, 2021 shares	Mar. 27, 2020 USD ($)	Jan. 01, 2020
Equity Class Of Treasury Stock [Line Items]
Number of locations | Location		79
Common Stock, Shares Authorized | shares		200,000,000	200,000,000
Minimum number of shares that company is required to repurchase | shares		0
Retained earnings net of tax after transitional charges		$ 1,121,945,000	$ 981,675,000			$ 466,000
Minimum number of days to consider the loans as non-accrual		90 days
Amount of allowance for credit loss		$ 0	0
Other identifiable intangible assets, amortized period (years)		7 years
Goodwill and intangible assets with indefinite lives		$ 313,481,000	313,481,000
Impairment recorded		0	0	$ 0
Carrying amount of goodwill arising from acquisitions, is deductible for federal income tax purposes		$ 11,233,000	13,640,000
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 gains in available-for-sale securities, included in accumulated other comprehensive income		$ (535,228,000)	99,253,000
First financial antidilutive securities excluded from eps computation | shares		1,261,000		399,300
Average Price of share repurchase | $ / shares	$ 24.75	$ 38.61
Commitments to Extend Credit [Member]
Equity Class Of Treasury Stock [Line Items]
Reserve for unfunded commitments		$ 12,323,000	6,436,000
Held-to-maturity Securities [Member]
Equity Class Of Treasury Stock [Line Items]
Securities held to maturity		0	$ 0
Allowance for Credit Losses [Member]
Equity Class Of Treasury Stock [Line Items]
Increase (decrease) in valuation and qualifying accounts and reserves from adjustment		619,000
Reserve for Unfunded Commitments [Member]
Equity Class Of Treasury Stock [Line Items]
Increase (decrease) in valuation and qualifying accounts and reserves from adjustment		$ 1,208,000
Cumulative Effect, Period of Adoption, Adjustment [Member]
Equity Class Of Treasury Stock [Line Items]
Retained earnings net of tax after transitional charges						$ 589,000
Commercial Bancshares Inc and Commercial State Bank [Member]
Equity Class Of Treasury Stock [Line Items]
Percentage of common stock acquired							100.00%
Common Stock [Member]
Equity Class Of Treasury Stock [Line Items]
Shares repurchased under stock repurchase authorization, shares | shares	324,802	244,559
Maximum [Member]
Equity Class Of Treasury Stock [Line Items]
Stock repurchase program, number of shares authorized to be repurchased | shares	5,000,000				4,000,000