Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended		7 Months Ended	11 Months Ended
	Dec. 31, 2024	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Nov. 30, 2024	Mar. 31, 2025	Feb. 28, 2025
Intangible Assets Goodwill And Other Assets [Line Items]
Goodwill	$ 1,100,000,000	$ 1,600,000,000		$ 1,600,000,000		$ 1,600,000,000
Other intangible assets	27,255,000	172,233,000		172,233,000		172,233,000
Amortization of core deposit and customer list intangible assets		9,200,000	$ 2,100,000	13,400,000	$ 4,200,000
Goodwill, impairment loss	$ 0					0	$ 0
Premier Financial Corporation [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Goodwill		476,175,000		476,175,000		476,175,000		$ 483,397,000	$ 476,175,000
Community Banking [Member] | Premier Financial Corporation [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Goodwill		476,200,000		476,200,000		476,200,000
Other intangible assets		151,500,000		151,500,000		151,500,000
Trust and Investment Services [Member] | Premier Financial Corporation [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Customer list intangibles		$ 6,900,000		$ 6,900,000		$ 6,900,000
Minimum [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible asset, useful life		10 years		10 years		10 years
Maximum [Member]
Intangible Assets Goodwill And Other Assets [Line Items]
Intangible asset, useful life		16 years		16 years		16 years