Regulatory Matters - Summary of Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Northrim Bank
Common equity tier 1 capital (to risk-weighted assets)
Common equity tier 1 capital (to risk-weighted assets), actual amount		$ 198,034	$ 189,447
Common equity tier 1 capital (to risk-weighted assets), actual ratio		10.59%	11.43%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount		$ 84,150	$ 74,585
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		$ 121,551	$ 107,735
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		$ 213,745	$ 201,087
Total Capital (to risk-weighted assets), actual ratio		0.1142	0.1213
Total Capital (to risk-weighted assets), adequately-capitalized amount		$ 149,734	$ 132,621
Total Capital (to risk-weighted assets), adequately-capitalized ratio		0.08	0.08
Total Capital (to risk-weighted assets), well-capitalized amount		$ 187,167	$ 165,777
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		$ 197,937	$ 189,348
Tier 1 Capital (to risk-weighted assets), actual ratio		0.1058	0.1142
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount		$ 112,252	$ 99,482
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio		0.06	0.06
Tier 1 Capital (to risk-weighted assets), well-capitalized amount		$ 149,669	$ 132,643
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		$ 197,937	$ 189,348
Tier I Capital (to average assets), actual ratio		0.0742	0.0731
Tier I Capital (to average assets), adequately-capitalized amount		$ 106,705	$ 103,610
Tier 1 capital (to average assets), adequately-capitalized ratio		0.04	0.04
Tier I Capital (to average assets), well-capitalized amount		$ 133,381	$ 129,513
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	$ 231,920	$ 225,412
Common equity tier 1 capital (to risk-weighted assets), actual ratio	12.29%	13.50%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount	$ 84,918	$ 75,137
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	$ 257,425	$ 246,836
Total Capital (to risk-weighted assets), actual ratio	0.1364	0.1479
Total Capital (to risk-weighted assets), adequately-capitalized amount	$ 150,982	$ 133,515
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	$ 241,617	$ 235,097
Tier 1 Capital (to risk-weighted assets), actual ratio	0.1281	0.1408
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount	$ 113,170	$ 100,183
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	$ 241,617	$ 235,097
Tier I Capital (to average assets), actual ratio	0.0901	0.0903
Tier I Capital (to average assets), adequately-capitalized amount	$ 107,266	$ 104,140
Tier 1 capital (to average assets), adequately-capitalized ratio	0.04	0.04