Regulatory Matters (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Jun. 30, 2003	Dec. 31, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 common equity capital required for capital adequacy to risk based assets		4.50%
Tier I capital (to average assets), adequately-capitalized ratio		4.00%
Total capital (to risk-weighted assets), adequately-capitalized ratio		8.00%
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio		6.00%
Tier 1 common equity (to risk-weighted assets), adequately capitalized ratio, conservation buffer		2.50%
Trust preferred securities offerings completed	$ 18,000	$ 18,000	$ 18,000
Northrim Bancorp, Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 common equity capital required for capital adequacy to risk based assets		4.50%
Tier I capital (to average assets), adequately-capitalized ratio		4.00%	4.00%
Total capital (to risk-weighted assets), adequately-capitalized ratio		8.00%	8.00%
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio		6.00%	4.00%
Tier 1 common equity (to risk-weighted assets), actual amount		$ 154,464
Tier 1 common equity (to risk-weighted assets), actual ratio		12.01%
Tier 1 common equity (to risk-weighted assets), adequately-capitalized amount		$ 57,876
Tier 1 common equity (to risk-weighted assets), well-capitalized amount		$ 83,598
Tier 1 common equity (to risk-weighted assets), well-capitalized ratio		6.50%
Total capital (to risk-weighted assets), actual amount		$ 187,761	$ 175,256
Total capital (to risk-weighted assets), actual ratio		14.60%	14.31%
Total capital (to risk-weighted assets), adequately-capitalized amount		$ 102,883	$ 97,977
Total capital (to risk-weighted assets), well-capitalized amount		$ 128,603	$ 122,471
Total capital (to risk-weighted assets), well-capitalized ratio		10.00%	10.00%
Tier 1 capital (to risk-weighted assets), actual amount		$ 171,653	$ 159,925
Tier 1 capital (to risk-weighted assets), actual ratio		13.34%	13.06%
Tier 1 capital (to risk-weighted assets), adequately-capitalized amount		$ 77,205	$ 48,982
Tier 1 capital (to risk-weighted assets), well-capitalized amount		$ 102,940	$ 73,472
Tier 1 capital (to risk-weighted assets), well-capitalized ratio		8.00%	6.00%
Tier I capital (to average assets), actual amount		$ 171,653	$ 159,925
Tier I capital (to average assets), actual ratio		11.20%	11.21%
Tier I capital (to average assets), adequately-capitalized amount		$ 61,305	$ 57,065
Tier I capital (to average assets), well-capitalized amount		$ 76,631	$ 71,331
Tier I capital (to average assets), well-capitalized ratio		5.00%	5.00%
Northrim Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 common equity capital required for capital adequacy to risk based assets		4.50%
Tier I capital (to average assets), adequately-capitalized ratio		4.00%	4.00%
Total capital (to risk-weighted assets), adequately-capitalized ratio		8.00%	8.00%
Tier 1 capital (to risk-weighted assets), adequately capitalized ratio		6.00%	4.00%
Tier 1 common equity (to risk-weighted assets), actual amount		$ 156,317
Tier 1 common equity (to risk-weighted assets), actual ratio		12.21%
Tier 1 common equity (to risk-weighted assets), adequately-capitalized amount		$ 57,611
Tier 1 common equity (to risk-weighted assets), well-capitalized amount		$ 83,215
Tier 1 common equity (to risk-weighted assets), well-capitalized ratio		6.50%
Total capital (to risk-weighted assets), actual amount		$ 171,662	$ 162,125
Total capital (to risk-weighted assets), actual ratio		13.41%	13.30%
Total capital (to risk-weighted assets), adequately-capitalized amount		$ 102,408	$ 97,519
Total capital (to risk-weighted assets), well-capitalized amount		$ 128,010	$ 121,898
Total capital (to risk-weighted assets), well-capitalized ratio		10.00%	10.00%
Tier 1 capital (to risk-weighted assets), actual amount		$ 155,630	$ 146,869
Tier 1 capital (to risk-weighted assets), actual ratio		12.16%	12.05%
Tier 1 capital (to risk-weighted assets), adequately-capitalized amount		$ 76,791	$ 48,753
Tier 1 capital (to risk-weighted assets), well-capitalized amount		$ 102,388	$ 73,130
Tier 1 capital (to risk-weighted assets), well-capitalized ratio		8.00%	6.00%
Tier I capital (to average assets), actual amount		$ 155,630	$ 146,869
Tier I capital (to average assets), actual ratio		10.18%	10.35%
Tier I capital (to average assets), adequately-capitalized amount		$ 61,151	$ 56,761
Tier I capital (to average assets), well-capitalized amount		$ 76,439	$ 70,951
Tier I capital (to average assets), well-capitalized ratio		5.00%	5.00%

Tier One Common Equity Capital

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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 for Capital Adequacy to Risk Based Assets, Conservation Buffer

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The cash inflow from issuance of trust preferred securities, net of the cash outflow for repurchasing trust preferred securities, by a business trust or other special purpose entity, mainly established by a bank holding entity, to third party investors. The trust's assets are deeply subordinated debentures of the bank holding entity. Most trust preferred securities are subject to a mandatory redemption upon the repayment of the debentures.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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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 amount of Tier 1 Risk Based Capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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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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The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) 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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