Goodwill and Other Intangible Assets - Gross Carrying Value and Accumulated Amortization of Other Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 461,000	$ 461,000
Accumulated Amortization	145,029	126,699
Net Carrying Amount	315,971	334,301
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	328,837	328,837
Accumulated Amortization	87,585	76,795
Net Carrying Amount	241,252	252,042
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	122,063	122,063
Accumulated Amortization	53,716	47,186
Net Carrying Amount	68,347	74,877
Non-competition agreement
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,000	4,000
Accumulated Amortization	2,000	1,600
Net Carrying Amount	2,000	2,400
Trade name
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,100	6,100
Accumulated Amortization	1,728	1,118
Net Carrying Amount	$ 4,372	$ 4,982