Regulatory Matters - Summary of Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Northrim Bank
Common equity tier 1 capital (to risk-weighted assets)
Common equity tier 1 capital (to risk-weighted assets), actual amount		$ 210,179	$ 198,034
Common equity tier 1 capital (to risk-weighted assets), actual ratio		9.89%	10.59%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount		$ 95,633	$ 84,150
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized ratio		4.50%	4.50%
Common equity tier 1 capital (to risk-weighted assets), well-capitalized amount		$ 138,136	$ 121,551
Common equity tier 1 capital (to risk-weighted assets), well-capitalized ratio		6.50%	6.50%
Total Capital (to risk-weighted assets)
Total Capital (to risk-weighted assets), actual amount		$ 229,772	$ 213,745
Total Capital (to risk-weighted assets), actual ratio		0.1081	0.1142
Total Capital (to risk-weighted assets), adequately-capitalized amount		$ 170,044	$ 149,734
Total Capital (to risk-weighted assets), adequately-capitalized ratio		0.08	0.08
Total Capital (to risk-weighted assets), well-capitalized amount		$ 212,555	$ 187,167
Total Capital (to risk-weighted assets), well-capitalized ratio		0.10	0.10
Tier I Capital (to risk-weighted assets)
Tier 1 Capital (to risk-weighted assets), actual amount		$ 210,084	$ 197,937
Tier 1 Capital (to risk-weighted assets), actual ratio		0.0988	0.1058
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount		$ 127,581	$ 112,252
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio		0.06	0.06
Tier 1 Capital (to risk-weighted assets), well-capitalized amount		$ 170,109	$ 149,669
Tier 1 Capital (to risk-weighted assets), well-capitalized ratio		0.08	0.08
Tier I Capital (to average assets)
Tier I Capital (to average assets), actual amount		$ 210,084	$ 197,937
Tier I Capital (to average assets), actual ratio		0.0751	0.0742
Tier I Capital (to average assets), adequately-capitalized amount		$ 111,896	$ 106,705
Tier 1 capital (to average assets), adequately-capitalized ratio		0.04	0.04
Tier I Capital (to average assets), well-capitalized amount		$ 139,870	$ 133,381
Tier I Capital (to average assets), well-capitalized ratio		0.05	0.05
Northrim Bancorp, Inc.
Common equity tier 1 capital (to risk-weighted assets)
Common equity tier 1 capital (to risk-weighted assets), actual amount	$ 235,378	$ 231,920
Common equity tier 1 capital (to risk-weighted assets), actual ratio	10.98%	12.29%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount	$ 96,466	$ 84,918
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized ratio	4.50%	4.50%
Total Capital (to risk-weighted assets)
Total Capital (to risk-weighted assets), actual amount	$ 264,775	$ 257,425
Total Capital (to risk-weighted assets), actual ratio	0.1235	0.1364
Total Capital (to risk-weighted assets), adequately-capitalized amount	$ 171,514	$ 150,982
Total Capital (to risk-weighted assets), adequately-capitalized ratio	0.08	0.08
Tier I Capital (to risk-weighted assets)
Tier 1 Capital (to risk-weighted assets), actual amount	$ 245,087	$ 241,617
Tier 1 Capital (to risk-weighted assets), actual ratio	0.1143	0.1281
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount	$ 128,655	$ 113,170
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio	0.06	0.06
Tier I Capital (to average assets)
Tier I Capital (to average assets), actual amount	$ 245,087	$ 241,617
Tier I Capital (to average assets), actual ratio	0.0872	0.0901
Tier I Capital (to average assets), adequately-capitalized amount	$ 112,425	$ 107,266
Tier 1 capital (to average assets), adequately-capitalized ratio	0.04	0.04