Regulatory Matters (Details) (USD $)	3 Months Ended	12 Months Ended
Jun. 30, 2003	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Trust preferred securities offerings completed	$ 18,000,000	$ 18,000,000	$ 18,000,000
Northrim Bancorp, Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital (to risk-weighted assets), Actual Amount		175,256,000	168,587,000
Total Capital (to risk-weighted assets), Actual Ratio		14.31%	16.61%
Total Capital (to risk-weighted assets), Adequately-Capitalized Amount		97,977,000	81,198,000
Total Capital (to risk-weighted assets), Adequately-Capitalized Ratio		8.00%	8.00%
Total Capital (to risk-weighted assets), Well-Capitalized Amount		122,471,000	101,497,000
Total Capital (to risk-weighted assets), Well-Capitalized Ratio		10.00%	10.00%
Tier 1 Capital (to risk-weighted assets), Actual Amount		159,925,000	155,851,000
Tier 1 Capital (to risk-weighted assets), Actual Ratio		13.06%	15.35%
Tier 1 Capital (to risk-weighted assets), Adequately-Capitalized Amount		48,982,000	40,613,000
Tier 1 Capital (to risk-weighted assets), Adequately Capitalized Ratio		4.00%	4.00%
Tier 1 Capital (to risk-weighted assets), Well-Capitalized Amount		73,472,000	60,919,000
Tier 1 Capital (to risk-weighted assets), Well-Capitalized Ratio		6.00%	6.00%
Tier I Capital (to average assets), Actual Amount		159,925,000	155,851,000
Tier I Capital (to average assets), Actual Ratio		11.21%	13.06%
Tier I Capital (to average assets), Adequately-Capitalized Amount		57,065,000	47,734,000
Tier I Capital (to average assets), Adequately-Capitalized Ratio		4.00%	4.00%
Tier I Capital (to average assets), Well-Capitalized Amount		71,331,000	59,667,000
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]
Total Capital (to risk-weighted assets), Actual Amount		162,125,000	151,308,000
Total Capital (to risk-weighted assets), Actual Ratio		13.30%	15.00%
Total Capital (to risk-weighted assets), Adequately-Capitalized Amount		97,519,000	80,698,000
Total Capital (to risk-weighted assets), Adequately-Capitalized Ratio		8.00%	8.00%
Total Capital (to risk-weighted assets), Well-Capitalized Amount		121,898,000	100,872,000
Total Capital (to risk-weighted assets), Well-Capitalized Ratio		10.00%	10.00%
Tier 1 Capital (to risk-weighted assets), Actual Amount		146,869,000	138,650,000
Tier 1 Capital (to risk-weighted assets), Actual Ratio		12.05%	13.75%
Tier 1 Capital (to risk-weighted assets), Adequately-Capitalized Amount		48,753,000	40,335,000
Tier 1 Capital (to risk-weighted assets), Adequately Capitalized Ratio		4.00%	4.00%
Tier 1 Capital (to risk-weighted assets), Well-Capitalized Amount		73,130,000	60,502,000
Tier 1 Capital (to risk-weighted assets), Well-Capitalized Ratio		6.00%	6.00%
Tier I Capital (to average assets), Actual Amount		146,869,000	138,650,000
Tier I Capital (to average assets), Actual Ratio		10.35%	11.68%
Tier I Capital (to average assets), Adequately-Capitalized Amount		56,761,000	47,483,000
Tier I Capital (to average assets), Adequately-Capitalized Ratio		4.00%	4.00%
Tier I Capital (to average assets), Well-Capitalized Amount		$ 70,951,000	$ 59,354,000
Tier I Capital (to average assets), Well-Capitalized Ratio		5.00%	5.00%
Forecast
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 1 Common Equity Capital Required for Capital Adequacy to Risk Based Assets, Conservation Buffer				2.50%
Total Capital (to risk-weighted assets), Adequately-Capitalized Ratio				8.00%
Tier 1 Capital (to risk-weighted assets), Adequately Capitalized Ratio				6.00%
Tier I Capital (to average assets), Adequately-Capitalized Ratio				4.00%

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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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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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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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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