Regulatory Matters - Summary of Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Northrim Bank
Common equity tier 1 capital (to risk-weighted assets)
Common equity tier 1 capital (to risk-weighted assets), actual amount		$ 218,664	$ 210,179
Common equity tier 1 capital (to risk-weighted assets), actual ratio		9.20%	9.89%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount		$ 106,955	$ 95,633
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		$ 154,491	$ 138,136
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		$ 246,643	$ 229,772
Total Capital (to risk-weighted assets), actual ratio		0.1037	0.1081
Total Capital (to risk-weighted assets), adequately-capitalized amount		$ 190,274	$ 170,044
Total Capital (to risk-weighted assets), adequately-capitalized ratio		0.08	0.08
Total Capital (to risk-weighted assets), well-capitalized amount		$ 237,843	$ 212,555
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		$ 218,664	$ 210,084
Tier 1 Capital (to risk-weighted assets), actual ratio		0.0920	0.0988
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount		$ 142,607	$ 127,581
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio		0.06	0.06
Tier 1 Capital (to risk-weighted assets), well-capitalized amount		$ 190,143	$ 170,109
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		$ 218,664	$ 210,084
Tier I Capital (to average assets), actual ratio		0.0724	0.0751
Tier I Capital (to average assets), adequately-capitalized amount		$ 120,809	$ 111,896
Tier 1 capital (to average assets), adequately-capitalized ratio		0.04	0.04
Tier I Capital (to average assets), well-capitalized amount		$ 151,011	$ 139,870
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	$ 223,362	$ 235,378
Common equity tier 1 capital (to risk-weighted assets), actual ratio	9.36%	10.98%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount	$ 107,386	$ 96,466
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	$ 261,059	$ 264,775
Total Capital (to risk-weighted assets), actual ratio	0.1094	0.1235
Total Capital (to risk-weighted assets), adequately-capitalized amount	$ 190,902	$ 171,514
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	$ 233,080	$ 245,087
Tier 1 Capital (to risk-weighted assets), actual ratio	0.0976	0.1143
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount	$ 143,287	$ 128,655
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	$ 233,080	$ 245,087
Tier I Capital (to average assets), actual ratio	0.0768	0.0872
Tier I Capital (to average assets), adequately-capitalized amount	$ 121,396	$ 112,425
Tier 1 capital (to average assets), adequately-capitalized ratio	0.04	0.04