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Allowance for Credit Losses - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Allowance for Credit Loss [Line Items]
Reserve for unfunded credits	$ 13,746,000	$ 5,981,000
Allowance for credit loss, completion of revision, period from forecast start date	5 years
Adjustment of allowance for credit loss related to merger	$ 24,800,000
General allowance for loan and lease losses	173,400,000	107,500,000
Increase (decrease) in general portion of the allowance for loan and lease losses	65,900,000
Increase (decrease) in allowance for credit loss	80,000,000.0
Specific allowance for loan and lease losses	79,400,000	17,500,000
Specific allowance for loan and lease losses period increase (decrease)	61,900,000
Total Loans and Leases	18,029,552,000	9,779,288,000
Interest income on nonaccrual loans	0	0
Holdco Merger
Financing Receivable, Allowance for Credit Loss [Line Items]
Specific allowance for loan and lease losses period increase (decrease)	44,800,000
Legacy Berkshire Portfolio
Financing Receivable, Allowance for Credit Loss [Line Items]
Adjustment of allowance for credit loss related to merger	5,600,000
Definite Loss
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans and Leases		0
Commercial Real Estate Loans | Holdco Merger
Financing Receivable, Allowance for Credit Loss [Line Items]
Specific allowance for loan and lease losses period increase (decrease)	26,400,000
C&I Loans | Holdco Merger
Financing Receivable, Allowance for Credit Loss [Line Items]
Specific allowance for loan and lease losses period increase (decrease)	18,200,000
Consumer Loans | Holdco Merger
Financing Receivable, Allowance for Credit Loss [Line Items]
Specific allowance for loan and lease losses period increase (decrease)	200,000
Commercial Loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans and Leases	2,784,152,000	1,211,714,000
Equipment financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans and Leases	1,163,211,000	1,294,950,000
Total
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans and Leases	14,100,820,000	$ 8,287,145,000
Total | Definite Loss
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans and Leases	$ 0
Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss, start of revision, period from forecast start date	2 years
Maximum
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss, start of revision, period from forecast start date	3 years

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Financing Receivable, Excluding Accrued Interest, Allowance For Credit Loss, Acquired In Business Combination

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

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Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

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