Loans and Allowance for Credit Losses - Narrative (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($) loan	Sep. 30, 2023 USD ($) loan	Sep. 30, 2024 USD ($) loan	Sep. 30, 2023 USD ($) loan	Dec. 31, 2023 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 17,336,040,000		$ 17,336,040,000		$ 16,845,670,000
Loan premiums and discounts			9,000,000.0		13,200,000
Deferred origination costs and fees	10,100,000		10,100,000		6,500,000
Financing receivable, accrued interest excluded from amortized costs	83,900,000		83,900,000		77,100,000
Nonaccrual loans with no allowance for credit loss	$ 4,800,000		$ 4,800,000		3,200,000
Number of loan modifications | loan	1		1
Loan modified and subsequently defaulted			$ 23,000
Number of loan modifications with payment default | loan		0		0
Financing receivable, collateral dependent, amount	$ 109,648,000		$ 109,648,000		144,604,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, term of loan			1 year
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, term of loan			3 years
Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans in process of foreclosure, amount	5,000,000		$ 5,000,000		2,500,000
OREO Received in Full or Partial Satisfaction of Loans | Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Foreclosed assets and other real estate owned	575,000		575,000		506,000
Unfunded Loan Commitment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unfunded commitments, allowance for credit loss	25,600,000		25,600,000		25,600,000
Reserve for unfunded commitments, released	0	$ 11,300,000	0	$ 16,300,000
Paycheck Protection Program Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 2,400,000		$ 2,400,000		$ 4,800,000