Acquisitions - Schedule of Recognized Identified Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	May 01, 2022	Dec. 01, 2021	Apr. 01, 2020	Dec. 31, 2022	Dec. 31, 2021
Liabilities assumed:
Goodwill recorded at merger				$ 110,715	$ 85,324
Roselle Entities
Assets acquired:
Cash and cash equivalents			$ 155,248
Debt securities available for sale			51,479
Debt securities held to maturity			13,418
Equity securities			1,796
Federal Home Loan Bank stock			2,010
Loans receivable			171,593
Accrued interest receivable			679
Office properties and equipment, net			5,774
Bank-owned life insurance			17,245
Deferred tax assets, net			1,334
Other assets			1,489
Total assets acquired			422,065
Liabilities assumed:
Deposits			333,234
Borrowings			37,728
Advance payments by borrowers for taxes and insurance			982
Accrued expenses and other liabilities			5,400
Total liabilities assumed			377,344
Net assets acquired			44,721
Fair market value of stock issued to Columbia Bank MHC for purchase			68,530
Goodwill recorded at merger			$ 23,809	17,600
Freehold Entities
Assets acquired:
Cash and cash equivalents		$ 20,417
Debt securities available for sale		118,017
Federal Home Loan Bank stock		3,032
Loans receivable		158,912
Accrued interest receivable		867
Office properties and equipment, net		5,934
Bank-owned life insurance		8,661
Deferred tax assets, net		454
Core deposit intangibles		42
Other assets		162
Total assets acquired		316,498
Liabilities assumed:
Deposits		210,117
Borrowings		59,908
Advance payments by borrowers for taxes and insurance		495
Accrued expenses and other liabilities		4,822
Total liabilities assumed		275,342
Net assets acquired		41,156
Fair market value of stock issued to Columbia Bank MHC for purchase		47,260
Goodwill recorded at merger		$ 6,104		6,000
RSI Entities
Assets acquired:
Cash and cash equivalents	$ 140,769
Debt securities available for sale	79,024
Equity securities	1,075
Federal Home Loan Bank stock	906
Loans receivable	335,501
Accrued interest receivable	910
Office properties and equipment, net	7,296
Bank-owned life insurance	13,033
Deferred tax assets, net	3,633
Core deposit intangibles	10,271
Other assets	2,723
Total assets acquired	595,141
Liabilities assumed:
Deposits	502,732
Borrowings	5,762
Advance payments by borrowers for taxes and insurance	1,341
Accrued expenses and other liabilities	10,568
Total liabilities assumed	520,403
Net assets acquired	74,738
Fair market value of stock issued to Columbia Bank MHC for purchase	102,741
Goodwill recorded at merger	$ 28,003			$ 25,500