Segment Information - Schedule of Segment Information (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017 USD ($) segment bank	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of segments | segment	2
Interest income	$ 14,465	$ 14,818
Interest expense	632	644
Net Interest Income	13,833	14,174
Provision for loan losses	400	703
Other operating income	8,896	9,105
Compensation expense - RML acquisition payments	174	130
Other operating expense	16,432	17,241
Income Before Provision for Income Taxes	5,723	5,205
Provision for income taxes	1,801	1,699
Net Income	3,922	3,506
Less: Net income attributable to the noncontrolling interest	97	130	$ 579
Net Income Attributable to Northrim BanCorp, Inc.	3,825	3,376	14,411
Total assets	1,512,580		1,526,540
Loans held for sale	$ 28,028		43,596
Community Banking
Segment Reporting Information [Line Items]
Number of branches | bank	14
Interest income	$ 14,115	14,448
Interest expense	566	515
Net Interest Income	13,549	13,933
Provision for loan losses	400	703
Other operating income	3,446	3,409
Compensation expense - RML acquisition payments	174	130
Other operating expense	11,613	12,306
Income Before Provision for Income Taxes	4,808	4,203
Provision for income taxes	1,422	1,285
Net Income	3,386	2,918
Less: Net income attributable to the noncontrolling interest	97	130
Net Income Attributable to Northrim BanCorp, Inc.	3,289	2,788
Total assets	1,464,589		1,459,950
Loans held for sale	0		0
Home Mortgage Lending
Segment Reporting Information [Line Items]
Interest income	350	370
Interest expense	66	129
Net Interest Income	284	241
Provision for loan losses	0	0
Other operating income	5,450	5,696
Compensation expense - RML acquisition payments	0	0
Other operating expense	4,819	4,935
Income Before Provision for Income Taxes	915	1,002
Provision for income taxes	379	414
Net Income	536	588
Less: Net income attributable to the noncontrolling interest	0	0
Net Income Attributable to Northrim BanCorp, Inc.	536	$ 588
Total assets	47,991		66,590
Loans held for sale	$ 28,028		$ 43,596