Stockholders' Equity - Actual Capital Amounts and Ratios (Details) $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Parent Company
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer, ratio	2.50%
Actual, Amount
Total capital	$ 1,120,849	$ 1,145,331
Tier one capital	1,060,490	1,085,665
Common equity tier one capital	1,053,273	1,078,448
Tier one leverage capital	$ 1,060,490	$ 1,085,665
Ratio, Actual
Capital to risk weighted assets	0.1408	0.1539
Tier one risk based capital to risk weighted assets	0.1332	0.1459
Common equity tier one capital	0.1323	0.1449
Tier one leverage capital to average assets	0.1004	0.1068
Minimum Capital Adequacy Requirements, Amount
Capital required for capital adequacy	$ 636,767	$ 595,313
Tier one risk based capital required for capital adequacy	477,575	446,484
Common equity tier one capital required for capital adequacy	358,182	334,863
Tier one leverage capital required for capital adequacy	$ 422,441	$ 406,643
Minimum Capital Adequacy Requirements, Ratio
Capital required for capital adequacy to risk weighted assets	0.0800	0.0800
Tier one risk based capital required for capital adequacy to risk weighted assets	0.060	0.0600
Common equity tier one capital required for capital adequacy to risk weighted assets	0.0450	0.0450
Tier one leverage capital required for capital adequacy to average assets	0.040	0.0400
Minimum Capital Adequacy Requirements With Capital Conservation Buffer, Amount
Capital required for capital adequacy with capital buffer	$ 835,757	$ 781,348
Tier one risk based capital required for capital adequacy with capital buffer	676,565	632,520
Common equity tier one risk based capital required for capital adequacy with capital buffer	557,171	520,899
Tier one leverage capital required for capital adequacy with capital buffer to average assets	$ 422,441	$ 406,643
Minimum Capital Adequacy Requirements With Capital Conservation Buffer, Ratio
Capital required for capital adequacy with capital buffer to risk weighted assets	0.1050	0.1050
Tier one risk based capital required for capital adequacy with capital buffer to risk weighted assets	0.0850	0.0850
Common equity tier one risk based capital requirement for capital adequacy with capital buffer to risk weighted assets	0.0700	0.0700
Tier one leverage capital requirement for capital adequacy with capital buffer to average assets	4.00%	4.00%
Columbia Bank
Actual, Amount
Total capital	$ 1,033,138	$ 1,019,850
Tier one capital	974,127	961,613
Common equity tier one capital	974,127	961,613
Tier one leverage capital	$ 974,127	$ 961,613
Ratio, Actual
Capital to risk weighted assets	0.1402	0.1412
Tier one risk based capital to risk weighted assets	0.1322	0.1332
Common equity tier one capital	0.1322	0.1332
Tier one leverage capital to average assets	0.0948	0.0974
Minimum Capital Adequacy Requirements, Amount
Capital required for capital adequacy	$ 589,622	$ 577,656
Tier one risk based capital required for capital adequacy	442,217	433,242
Common equity tier one capital required for capital adequacy	331,663	324,931
Tier one leverage capital required for capital adequacy	$ 411,126	$ 394,968
Minimum Capital Adequacy Requirements, Ratio
Capital required for capital adequacy to risk weighted assets	0.0800	0.0800
Tier one risk based capital required for capital adequacy to risk weighted assets	0.0600	0.0600
Common equity tier one capital required for capital adequacy to risk weighted assets	0.0450	0.0450
Tier one leverage capital required for capital adequacy to average assets	0.0400	0.0400
Minimum Capital Adequacy Requirements With Capital Conservation Buffer, Amount
Capital required for capital adequacy with capital buffer	$ 773,879	$ 758,173
Tier one risk based capital required for capital adequacy with capital buffer	626,474	613,759
Common equity tier one risk based capital required for capital adequacy with capital buffer	515,920	505,449
Tier one leverage capital required for capital adequacy with capital buffer to average assets	$ 411,126	$ 394,968
Minimum Capital Adequacy Requirements With Capital Conservation Buffer, Ratio
Capital required for capital adequacy with capital buffer to risk weighted assets	0.1050	0.1050
Tier one risk based capital required for capital adequacy with capital buffer to risk weighted assets	0.0850	0.0850
Common equity tier one risk based capital requirement for capital adequacy with capital buffer to risk weighted assets	0.0700	0.0700
Tier one leverage capital requirement for capital adequacy with capital buffer to average assets	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount
Capital required to be well capitalized, amount	$ 737,028	$ 722,070
Tier one risk based capital required to be well capitalized, amount	589,622	577,656
Common equity tier one capital required to be well-capitalized, amount	479,068	469,345
Tier one leverage capital required to be well capitalized, amount	$ 513,908	$ 493,711
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio
Capital required to be well capitalized to risk weighted assets, ratio	0.1000	0.1000
Tier one risk based capital required to be well capitalized to risk weighted assets, ratio	0.080	0.0800
Common equity tier one capital required to be well-capitalized to risk weighted assets, ratio	0.0650	0.0650
Tier one leverage capital required to be well capitalized to average assets, ratio	0.0500	0.0500
Freehold Bank
Actual, Amount
Total capital	$ 45,417	$ 44,725
Tier one capital	44,045	43,298
Common equity tier one capital	44,045	43,298
Tier one leverage capital	$ 44,045	$ 43,298
Ratio, Actual
Capital to risk weighted assets	0.2250	0.2292
Tier one risk based capital to risk weighted assets	0.2182	0.2219
Common equity tier one capital	0.2182	0.2219
Tier one leverage capital to average assets	0.1527	0.1519
Minimum Capital Adequacy Requirements, Amount
Capital required for capital adequacy	$ 16,152	$ 15,609
Tier one risk based capital required for capital adequacy	12,114	11,706
Common equity tier one capital required for capital adequacy	9,085	8,780
Tier one leverage capital required for capital adequacy	$ 11,539	$ 11,399
Minimum Capital Adequacy Requirements, Ratio
Capital required for capital adequacy to risk weighted assets	0.0800	0.0800
Tier one risk based capital required for capital adequacy to risk weighted assets	0.0600	0.0600
Common equity tier one capital required for capital adequacy to risk weighted assets	0.0450	0.0450
Tier one leverage capital required for capital adequacy to average assets	0.0400	0.0400
Minimum Capital Adequacy Requirements With Capital Conservation Buffer, Amount
Capital required for capital adequacy with capital buffer	$ 21,199	$ 20,486
Tier one risk based capital required for capital adequacy with capital buffer	17,161	16,584
Common equity tier one risk based capital required for capital adequacy with capital buffer	14,133	13,657
Tier one leverage capital required for capital adequacy with capital buffer to average assets	$ 11,539	$ 11,399
Minimum Capital Adequacy Requirements With Capital Conservation Buffer, Ratio
Capital required for capital adequacy with capital buffer to risk weighted assets	0.1050	0.1050
Tier one risk based capital required for capital adequacy with capital buffer to risk weighted assets	0.0850	0.0850
Common equity tier one risk based capital requirement for capital adequacy with capital buffer to risk weighted assets	0.0700	0.0700
Tier one leverage capital requirement for capital adequacy with capital buffer to average assets	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount
Capital required to be well capitalized, amount	$ 20,189	$ 19,511
Tier one risk based capital required to be well capitalized, amount	16,152	15,609
Common equity tier one capital required to be well-capitalized, amount	13,123	12,682
Tier one leverage capital required to be well capitalized, amount	$ 14,424	$ 14,249
To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio
Capital required to be well capitalized to risk weighted assets, ratio	0.1000	0.1000
Tier one risk based capital required to be well capitalized to risk weighted assets, ratio	0.0800	0.0800
Common equity tier one capital required to be well-capitalized to risk weighted assets, ratio	0.0650	0.0650
Tier one leverage capital required to be well capitalized to average assets, ratio	0.0500	0.0500