Business Combinations - Narrative (Details)			2 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Jan. 06, 2022 USD ($) branch $ / shares shares	Dec. 31, 2023 USD ($) shares	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Business Acquisition [Line Items]
Assets	$ 11,176,809,000			$ 11,176,809,000		$ 11,176,809,000		$ 10,783,840,000
Loans	8,218,898,000			8,218,898,000		8,218,898,000		7,795,786,000
Deposits	8,602,503,000			8,602,503,000		8,602,503,000		$ 8,567,471,000
Merger-related expenses				198,000	$ 3,488,000	735,000	$ 8,073,000
Net PCD loans		$ 124,431,000
Provident Financial Services, Inc. (Combined) | Forecast
Business Acquisition [Line Items]
Assets			$ 25,000,000,000
Loans			18,000,000,000
Deposits			$ 20,000,000,000
Provident Financial Services, Inc. (Combined) | Provident Financial Services, Inc. | Forecast
Business Acquisition [Line Items]
Business combination, merger, shareholder interest in combined entity, ownership percentage			58.00%
Provident Financial Services, Inc. (Combined) | Lakeland Shareholders | Forecast
Business Acquisition [Line Items]
Business combination, merger, shareholder interest in combined entity, ownership percentage			42.00%
Lakeland Bancorp, Inc
Business Acquisition [Line Items]
Merger-related expenses				$ 198,000	3,500,000	$ 735,000	3,500,000
Lakeland Bancorp, Inc | Forecast
Business Acquisition [Line Items]
Business combination, consideration transferred			$ 1,300,000,000
Lakeland Bancorp, Inc | Provident Financial Services, Inc. | Forecast
Business Acquisition [Line Items]
Business combination, consideration transferred, equity interests issued and issuable, entity shares issued per acquiree share (in shares) | shares			0.8319
1st Constitution Bancorp
Business Acquisition [Line Items]
Business combination, consideration transferred, equity interests issued and issuable, entity shares issued per acquiree share (in shares) | shares		1.3577
Merger-related expenses					$ 0		$ 4,600,000
Number of operating bank branches | branch		25
Consideration paid through common stock (in shares) | shares		14,020,495
Business acquisition, share price (in usd per share) | $ / shares		$ 25.55
Business acquisition, average strike price (in usd per share) | $ / shares		$ 15.95
Business combination, consideration transferred, cash payments for equity interest		$ 559,000
Net PCD loans	$ 72,100,000