Loans - Narrative (Details)			3 Months Ended	12 Months Ended
	Mar. 31, 2024 USD ($) loan	Jan. 06, 2022 USD ($)	Mar. 31, 2024 USD ($) loan	Dec. 31, 2023 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable on loans	$ 29,500,000		$ 29,500,000	$ 29,100,000
Net deferred loan fees	(2,500,000)		(2,500,000)	(1,800,000)
Overdraft balances included in home equity and consumer loans	459,000		459,000	619,000
Loans pledged for actual and potential borrowings at the Federal Home Loan Bank	$ 4,640,000,000		$ 4,640,000,000	$ 4,580,000,000
Number of loans still accruing | loan	0		0	0
Net PCD loans		$ 124,431,000
Financing receivable, excluding accrued interest, modified in period, amount			$ 0	$ 0
1st Constitution Bancorp
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net PCD loans	$ 68,400,000
Residential And Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, nonaccrual, in the process of foreclosure	$ 659,000		$ 659,000	$ 621,000