| Document and Entity Information Document | Oct. 26, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 26, 2020 |
| Entity Registrant Name | Northrim BanCorp, Inc. |
| Entity Central Index Key | 0001163370 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | AK |
| Entity File Number | 0-33501 |
| Entity Tax Identification Number | 92-0175752 |
| Entity Address, Address Line One | 3111 C Street, |
| Entity Address, City or Town | Anchorage, |
| Entity Address, State or Province | AK |
| Entity Address, Postal Zip Code | 99503 |
| City Area Code | 907- |
| Local Phone Number | 562-0062 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
