Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		6 Months Ended		7 Months Ended	11 Months Ended
	Jun. 30, 2022 USD ($) shares	Jun. 30, 2021 USD ($) shares	Jun. 30, 2022 USD ($) Location shares	Jun. 30, 2021 USD ($) shares	Jul. 27, 2021 shares	Jun. 30, 2022 USD ($) shares	Dec. 31, 2021 USD ($)
Equity, Class of Treasury Stock [Line Items]
Number of locations | Location			78
Minimum number of shares that company is required to repurchase | shares					0
Amount of allowance for credit loss	$ 0	$ 0	$ 0	$ 0		$ 0	$ 0
Treasury Stock, Value, Acquired						9,450,000
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
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 (losses) in available-for-sale securities, included in accumulated other comprehensive income	400,514,000	136,486,000	$ 400,514,000	136,486,000		400,514,000	99,253,000
Retained earnings net of tax after transitional charges	$ 1,052,453,000	$ 910,171,000	$ 1,052,453,000	$ 910,171,000		$ 1,052,453,000	981,675,000
First financial antidilutive securities excluded from eps computation | shares	207,000	0	209,000	0
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Shares repurchased under stock repurchase authorization, shares | shares	(191,987)		(191,987)			244,559
Commitments to Extend Credit [Member]
Equity, Class of Treasury Stock [Line Items]
Reserve for unfunded commitments	$ 8,718,000,000	$ 6,751,000,000	$ 8,718,000,000	$ 6,751,000,000		$ 8,718,000,000	6,436,000,000
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