Regulatory Matters - Summary of Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Northrim Bancorp, Inc.
Tier One Common Equity Based Capital [Abstract]
Common equity tier 1 capital (to risk-weighted assets), actual amount	$ 190,807	$ 190,541
Common equity tier 1 capital (to risk-weighted assets), actual ratio	13.69%	14.73%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount	$ 62,720	$ 58,210
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized ratio	4.50%	4.50%
Capital [Abstract]
Total Capital (to risk-weighted assets), actual amount	$ 217,912	$ 216,410
Total Capital (to risk-weighted assets), actual ratio	15.63%	16.73%
Total Capital (to risk-weighted assets), adequately-capitalized amount	$ 111,535	$ 103,484
Total Capital (to risk-weighted assets), adequately-capitalized ratio	8.00%	8.00%
Tier One Risk Based Capital [Abstract]
Tier 1 Capital (to risk-weighted assets), actual amount	$ 200,465	$ 200,189
Tier 1 Capital (to risk-weighted assets), actual ratio	14.38%	15.47%
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount	$ 83,643	$ 77,643
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio	6.00%	6.00%
Tier One Leverage Capital [Abstract]
Tier I Capital (to average assets), actual amount	$ 200,465	$ 200,189
Tier I Capital (to average assets), actual ratio	12.41%	13.40%
Tier I Capital (to average assets), adequately-capitalized amount	$ 64,614	$ 59,758
Tier 1 capital (to average assets), adequately-capitalized ratio	4.00%	4.00%
Northrim Bank
Tier One Common Equity Based Capital [Abstract]
Common equity tier 1 capital (to risk-weighted assets), actual amount	$ 165,963	$ 166,580
Common equity tier 1 capital (to risk-weighted assets), actual ratio	11.98%	13.05%
Common equity tier 1 capital (to risk-weighted assets), adequately-capitalized amount	$ 62,340	$ 57,441
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	$ 90,047	$ 82,971
Common equity tier 1 capital (to risk-weighted assets), well-capitalized ratio	6.50%	6.50%
Capital [Abstract]
Total Capital (to risk-weighted assets), actual amount	$ 183,299	$ 182,585
Total Capital (to risk-weighted assets), actual ratio	13.24%	14.30%
Total Capital (to risk-weighted assets), adequately-capitalized amount	$ 110,755	$ 102,145
Total Capital (to risk-weighted assets), adequately-capitalized ratio	8.00%	8.00%
Total Capital (to risk-weighted assets), well-capitalized amount	$ 138,443	$ 127,682
Total Capital (to risk-weighted assets), well-capitalized ratio	10.00%	10.00%
Tier One Risk Based Capital [Abstract]
Tier 1 Capital (to risk-weighted assets), actual amount	$ 165,963	$ 166,580
Tier 1 Capital (to risk-weighted assets), actual ratio	11.98%	13.05%
Tier 1 Capital (to risk-weighted assets), adequately-capitalized amount	$ 83,120	$ 76,589
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio	6.00%	6.00%
Tier 1 Capital (to risk-weighted assets), well-capitalized amount	$ 110,827	$ 102,118
Tier 1 Capital (to risk-weighted assets), well-capitalized ratio	8.00%	8.00%
Tier One Leverage Capital [Abstract]
Tier I Capital (to average assets), actual amount	$ 165,963	$ 166,580
Tier I Capital (to average assets), actual ratio	10.36%	11.28%
Tier I Capital (to average assets), adequately-capitalized amount	$ 64,078	$ 59,071
Tier 1 capital (to average assets), adequately-capitalized ratio	4.00%	4.00%
Tier I Capital (to average assets), well-capitalized amount	$ 80,098	$ 73,839
Tier I Capital (to average assets), well-capitalized ratio	5.00%	5.00%

Tier One Common Equity Based Capital [Abstract]

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Tier One Common Equity Capital Required for Capital Adequacy

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Tier One Common Equity Capital Required for Capital Adequacy to Risk Based Assets

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Tier One Common Equity Capital Required to be Well Capitalized

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Tier One Common Equity Capital Required to be Well Capitalized to Risk Based Assets

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Tier One Common Equity Capital to Risk Based Assets

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The amount of total capital as defined in the regulations.

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The minimum amount of Total Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Total Capital required to be categorized as well as capitalized under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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Tier 1 Leverage Capital as defined in the regulations. Also called Core Capital.

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The minimum amount of Tier 1 Leverage Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The amount of Tier 1 Risk Based Capital required to be categorized as well capitalized under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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