Regulatory Matters - Summary of Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Northrim Bank
Common equity tier 1 capital (to risk-weighted assets)
Common equity tier 1 capital (to risk-weighted assets), actual amount		$ 311,964	$ 218,664
Common equity tier 1 capital (to risk-weighted assets), actual ratio		11.84%	9.20%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount		$ 118,567	$ 106,955
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		$ 171,264	$ 154,491
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		$ 337,124	$ 246,643
Total Capital (to risk-weighted assets), actual ratio		0.1279	0.1037
Total Capital (to risk-weighted assets), adequately-capitalized amount		$ 210,867	$ 190,274
Total Capital (to risk-weighted assets), adequately-capitalized ratio		0.08	0.08
Total Capital (to risk-weighted assets), well-capitalized amount		$ 263,584	$ 237,843
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		$ 311,964	$ 218,664
Tier 1 Capital (to risk-weighted assets), actual ratio		0.1184	0.0920
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount		$ 158,090	$ 142,607
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio		0.06	0.06
Tier 1 Capital (to risk-weighted assets), well-capitalized amount		$ 210,786	$ 190,143
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		$ 311,964	$ 218,664
Tier I Capital (to average assets), actual ratio		0.0961	0.0724
Tier I Capital (to average assets), adequately-capitalized amount		$ 129,850	$ 120,809
Tier 1 capital (to average assets), adequately-capitalized ratio		0.04	0.04
Tier I Capital (to average assets), well-capitalized amount		$ 162,312	$ 151,011
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	$ 275,363	$ 223,362
Common equity tier 1 capital (to risk-weighted assets), actual ratio	10.38%	9.36%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount	$ 119,377	$ 107,386
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	$ 370,333	$ 261,059
Total Capital (to risk-weighted assets), actual ratio	0.1395	0.1094
Total Capital (to risk-weighted assets), adequately-capitalized amount	$ 212,377	$ 190,902
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	$ 285,173	$ 233,080
Tier 1 Capital (to risk-weighted assets), actual ratio	0.1075	0.0976
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount	$ 159,166	$ 143,287
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	$ 285,173	$ 233,080
Tier I Capital (to average assets), actual ratio	0.0877	0.0768
Tier I Capital (to average assets), adequately-capitalized amount	$ 130,068	$ 121,396
Tier 1 capital (to average assets), adequately-capitalized ratio	0.04	0.04