Segment Information - Schedule of Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) bank	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment bank	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of segments | segment			2
Interest income	$ 14,892	$ 14,718	$ 29,357	$ 29,536
Interest expense	648	639	1,280	1,283
Net Interest Income	14,244	14,079	28,077	28,253
Provision for loan losses	300	200	700	903
Other operating income	9,718	11,864	18,614	20,969
Compensation expense - RML acquisition payments	0	687	174	817
Other operating expense	18,466	18,682	34,898	35,923
Income Before Provision for Income Taxes	5,196	6,374	10,919	11,579
Provision for income taxes	1,455	1,868	3,256	3,567
Net Income	3,741	4,506	7,663	8,012
Less: Net income attributable to the noncontrolling interest	152	156	249	286	$ 579
Net Income Attributable to Northrim BanCorp, Inc.	3,589	4,350	7,414	7,726	14,411
Total assets	1,493,205		1,493,205		1,526,540
Loans held for sale	$ 53,863		$ 53,863		43,596
Community Banking
Segment Reporting Information [Line Items]
Number of branches | bank	14		14
Interest income	$ 14,482	14,246	$ 28,597	28,694
Interest expense	529	417	1,095	932
Net Interest Income	13,953	13,829	27,502	27,762
Provision for loan losses	300	200	700	903
Other operating income	3,367	3,354	6,813	6,763
Compensation expense - RML acquisition payments		687	174	817
Other operating expense	13,240	12,504	24,853	24,810
Income Before Provision for Income Taxes	3,780	3,792	8,588	7,995
Provision for income taxes	871	805	2,293	2,090
Net Income	2,909	2,987	6,295	5,905
Less: Net income attributable to the noncontrolling interest	152	156	249	286
Net Income Attributable to Northrim BanCorp, Inc.	2,757	2,831	6,046	5,619
Total assets	1,417,828		1,417,828		1,459,950
Loans held for sale	0		0		0
Home Mortgage Lending
Segment Reporting Information [Line Items]
Interest income	410	472	760	842
Interest expense	119	222	185	351
Net Interest Income	291	250	575	491
Provision for loan losses	0	0	0	0
Other operating income	6,351	8,510	11,801	14,206
Compensation expense - RML acquisition payments		0	0	0
Other operating expense	5,226	6,178	10,045	11,113
Income Before Provision for Income Taxes	1,416	2,582	2,331	3,584
Provision for income taxes	584	1,063	963	1,477
Net Income	832	1,519	1,368	2,107
Less: Net income attributable to the noncontrolling interest	0	0	0	0
Net Income Attributable to Northrim BanCorp, Inc.	832	$ 1,519	1,368	$ 2,107
Total assets	75,377		75,377		66,590
Loans held for sale	$ 53,863		$ 53,863		$ 43,596