Loans - Narrative (Details)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2025 USD ($) loan	Sep. 30, 2025 USD ($) loan	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)	Jun. 30, 2024 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Purchased with Credit Deterioration, Discount (Premium)	$ 6,400,000			$ 7,800,000
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available	6,400,000,000	$ 6,400,000,000				$ 5,700,000,000
Proceeds from sale of SBA loans	22,200,000	78,000,000.0	$ 23,100,000
Gain on sale of SBA loans	1,100,000	4,188,000	1,415,000
Financing receivable, allowance for credit loss	148,854,000	148,854,000				137,950,000
Allowance for credit loss adjustment	37,000,000.0	37,000,000.0
Nonperforming loan balances, excluding government guaranteed balances	33,500,000	33,500,000				22,000,000.0
Loans, including unearned loan fees	$ 11,434,255,000	$ 11,434,255,000				11,082,405,000
Number of borrowing relationships affecting nonperforming loans | loan	2	2
Other Assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable	$ 56,500,000	$ 56,500,000				52,400,000
Enterprise Value Lending Portfolio Niche Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for credit loss adjustment	21,400,000	21,400,000
Non-Covered Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	148,854,000	148,854,000	139,778,000	134,771,000	$ 145,133,000	137,950,000	$ 139,464,000
Loans, including unearned loan fees	11,583,109,000	11,583,109,000				11,220,355,000
Non-Covered Loans | Enterprise Value Lending Portfolio Niche Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	27,500,000	27,500,000				14,500,000
Non-Covered Loans | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	71,503,000	71,503,000	$ 64,060,000	$ 58,886,000	$ 72,081,000	63,231,000	$ 61,478,000
Loans, including unearned loan fees	4,948,761,000	4,948,761,000				4,720,428,000
Residential | Consumer Mortgage Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans, including unearned loan fees	5,800,000	5,800,000				$ 0
Cumulative Effect, Period Of Adoption, Adjustment | Non-Covered Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss	$ 10,700,000	$ 10,700,000
Cumulative Effect, Period Of Adoption, Adjustment | Non-Covered Loans | Baseline
Accounts, Notes, Loans and Financing Receivable [Line Items]
Growth upside forecast	0.40	0.40
Cumulative Effect, Period Of Adoption, Adjustment | Non-Covered Loans | Near-term growth upside
Accounts, Notes, Loans and Financing Receivable [Line Items]
Growth upside forecast	0.30	0.30
Cumulative Effect, Period Of Adoption, Adjustment | Non-Covered Loans | Moderate recession downside
Accounts, Notes, Loans and Financing Receivable [Line Items]
Growth upside forecast	0.30	0.30