Segment Information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total interest income	$ 14,522	$ 14,860	$ 14,718	$ 14,818	$ 15,063	$ 15,388	$ 14,943	$ 14,386	$ 58,918	$ 59,780	$ 54,346
Interest expense	631	647	639	644	663	706	748	754	2,561	2,871	2,053
Net Interest Income	13,891	14,213	14,079	14,174	14,400	14,682	14,195	13,632	56,357	56,909	52,293
Provision (benefit) for loan losses	743	652	200	703	376	676	376	326	2,298	1,754	(636)
Other operating income	10,359	11,935	11,864	9,105	10,104	12,407	11,563	10,535	43,263	44,608	20,034
Compensation expense - RML acquisition payments	708	3,250	687	130	1,225	780	587	1,502	4,775	4,094	0
Other operating expense	17,646	17,936	18,682	17,241	17,004	17,423	17,166	16,959	71,505	68,551	46,923
Income Before Provision for Income Taxes	5,153	4,310	6,374	5,205	5,899	8,210	7,629	5,380	21,042	27,118	26,040
Provision for income taxes	1,458	1,027	1,868	1,699	1,673	2,678	2,686	1,747	6,052	8,784	8,173
Net Income	3,695	3,283	4,506	3,506	4,226	5,532	4,943	3,633	14,990	18,334	17,867
Less: Net income attributable to the noncontrolling interest	105	188	156	130	120	197	162	72	579	551	459
Net Income Attributable to Northrim BanCorp, Inc.	3,590	$ 3,095	$ 4,350	$ 3,376	4,106	$ 5,335	$ 4,781	$ 3,561	14,411	17,783	17,408
Total assets	1,526,540				1,499,492				1,526,540	1,499,492	1,449,349
Loans held for sale	43,596				50,553				43,596	50,553	43,866
Community Banking
Segment Reporting Information [Line Items]
Total interest income									56,986	57,729	54,204
Interest expense									1,739	1,796	1,942
Net Interest Income									55,247	55,933	52,262
Provision (benefit) for loan losses									2,298	1,754	(636)
Other operating income									13,756	14,995	16,754
Compensation expense - RML acquisition payments									4,775	4,094
Other operating expense									48,610	47,070	45,050
Income Before Provision for Income Taxes									13,320	18,010	24,602
Provision for income taxes									2,867	5,024	7,582
Net Income									10,453	12,986	17,020
Less: Net income attributable to the noncontrolling interest									579	551	459
Net Income Attributable to Northrim BanCorp, Inc.									9,874	12,435	16,561
Total assets	1,459,950				1,431,759				1,459,950	1,431,759	1,390,852
Loans held for sale	0				0				0	0	0
Home Mortgage Lending
Segment Reporting Information [Line Items]
Total interest income									1,932	2,051	142
Interest expense									822	1,075	111
Net Interest Income									1,110	976	31
Provision (benefit) for loan losses									0	0	0
Other operating income									29,507	29,613	3,280
Compensation expense - RML acquisition payments									0	0
Other operating expense									22,895	21,481	1,873
Income Before Provision for Income Taxes									7,722	9,108	1,438
Provision for income taxes									3,185	3,760	591
Net Income									4,537	5,348	847
Less: Net income attributable to the noncontrolling interest									0	0	0
Net Income Attributable to Northrim BanCorp, Inc.									4,537	5,348	847
Total assets	66,590				67,733				66,590	67,733	58,497
Loans held for sale	$ 43,596				$ 50,553				$ 43,596	$ 50,553	$ 43,866