Regulatory Matters - Summary of Capital Requirements (Details) - USD ($) $ in Thousands	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	$ 189,447	$ 178,532
Common equity tier 1 capital (to risk-weighted assets), actual ratio	11.43%	11.89%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount	$ 74,585	$ 67,569
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	$ 107,735	$ 97,599
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	$ 201,087	$ 197,233
Total Capital (to risk-weighted assets), actual ratio	0.1213	0.1313
Total Capital (to risk-weighted assets), adequately-capitalized amount	$ 132,621	$ 120,172
Total Capital (to risk-weighted assets), adequately-capitalized ratio	0.08	0.08
Total Capital (to risk-weighted assets), well-capitalized amount	$ 165,777	$ 150,216
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	$ 189,348	$ 178,429
Tier 1 Capital (to risk-weighted assets), actual ratio	0.1142	0.1188
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount	$ 99,482	$ 90,116
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio	0.06	0.06
Tier 1 Capital (to risk-weighted assets), well-capitalized amount	$ 132,643	$ 120,154
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	$ 189,348	$ 178,429
Tier I Capital (to average assets), actual ratio	0.0731	0.0855
Tier I Capital (to average assets), adequately-capitalized amount	$ 103,610	$ 83,476
Tier 1 capital (to average assets), adequately-capitalized ratio	0.04	0.04
Tier I Capital (to average assets), well-capitalized amount	$ 129,513	$ 104,344
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	$ 225,412	$ 205,717
Common equity tier 1 capital (to risk-weighted assets), actual ratio	13.50%	13.75%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount	$ 75,137	$ 67,326
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	$ 246,836	$ 234,363
Total Capital (to risk-weighted assets), actual ratio	0.1479	0.1546
Total Capital (to risk-weighted assets), adequately-capitalized amount	$ 133,515	$ 121,275
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	$ 235,097	$ 215,380
Tier 1 Capital (to risk-weighted assets), actual ratio	0.1408	0.1420
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount	$ 100,183	$ 91,006
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	$ 235,097	$ 215,380
Tier I Capital (to average assets), actual ratio	0.0903	0.1025
Tier I Capital (to average assets), adequately-capitalized amount	$ 104,140	$ 84,051
Tier 1 capital (to average assets), adequately-capitalized ratio	0.04	0.04