Segment Information - Schedule of Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($) bank	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) Segment bank	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of segments | Segment			2
Interest income	$ 14,718	$ 14,943	$ 29,536	$ 29,329
Interest expense	639	748	1,283	1,502
Net Interest Income	14,079	14,195	28,253	27,827
Provision for loan losses	200	376	903	702
Other operating income	11,864	11,563	20,969	22,098
Change in fair value, RML earn-out liability	687	587	817	2,089
Other operating expense	18,682	17,166	35,923	34,125
Income Before Provision for Income Taxes	6,374	7,629	11,579	13,009
Provision for income taxes	1,868	2,686	3,567	4,433
Net Income	4,506	4,943	8,012	8,576
Less: Net income attributable to the noncontrolling interest	156	162	286	234	$ 551
Net Income Attributable to Northrim BanCorp, Inc.	4,350	4,781	7,726	8,342	17,783
Total assets	1,518,370		1,518,370		1,499,492
Loans held for sale	$ 60,360		$ 60,360		50,553
Community Banking
Segment Reporting Information [Line Items]
Number of Stores | bank	14		14
Interest income	$ 14,246	14,354	$ 28,694	28,344
Interest expense	417	370	932	844
Net Interest Income	13,829	13,984	27,762	27,500
Provision for loan losses	200	376	903	702
Other operating income	3,354	3,704	6,763	6,933
Change in fair value, RML earn-out liability	687	587	817	2,089
Other operating expense	12,504	11,430	24,810	23,252
Income Before Provision for Income Taxes	3,792	5,295	7,995	8,390
Provision for income taxes	805	1,722	2,090	2,526
Net Income	2,987	3,573	5,905	5,864
Less: Net income attributable to the noncontrolling interest	156	162	286	234
Net Income Attributable to Northrim BanCorp, Inc.	2,831	3,411	5,619	5,630
Total assets	1,436,273		1,436,273		1,431,759
Loans held for sale	0		0		0
Home Mortgage Lending
Segment Reporting Information [Line Items]
Interest income	472	589	842	985
Interest expense	222	378	351	658
Net Interest Income	250	211	491	327
Provision for loan losses	0	0	0	0
Other operating income	8,510	7,859	14,206	15,165
Change in fair value, RML earn-out liability	0	0	0	0
Other operating expense	6,178	5,736	11,113	10,873
Income Before Provision for Income Taxes	2,582	2,334	3,584	4,619
Provision for income taxes	1,063	964	1,477	1,907
Net Income	1,519	1,370	2,107	2,712
Less: Net income attributable to the noncontrolling interest	0	0	0	0
Net Income Attributable to Northrim BanCorp, Inc.	1,519	$ 1,370	2,107	$ 2,712
Total assets	82,097		82,097		67,733
Loans held for sale	$ 60,360		$ 60,360		$ 50,553