Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Data [Abstract]
Total interest income	$ 15,063	$ 15,388	$ 14,943	$ 14,386	$ 14,566	$ 14,212	$ 13,895	$ 11,673	$ 59,780	$ 54,346	$ 46,074
Total interest expense	663	706	748	754	642	487	484	440	2,871	2,053	2,040
Net Interest Income	14,400	14,682	14,195	13,632	13,924	13,725	13,411	11,233	56,909	52,293	44,034
Provision for loan losses	376	676	376	326	500	0	(1,136)	0	1,754	(636)	(635)
Other operating income	10,104	12,407	11,563	10,535	9,376	4,934	4,106	2,734	44,608	21,149	12,886
Other operating expense	18,229	18,203	17,753	18,461	13,671	12,779	11,620	9,967	72,645	48,038	38,897
Income Before Provision for Income Taxes	5,899	8,210	7,629	5,380	9,129	5,880	7,033	4,000	27,118	26,040	18,658
Provision for income taxes	1,673	2,678	2,686	1,747	2,325	1,982	2,569	1,297	8,784	8,173	6,246
Net Income	4,226	5,532	4,943	3,633	6,804	3,898	4,464	2,703	18,334	17,867	12,412
Less: Net income attributable to the noncontrolling interest	120	197	162	72	130	191	95	45	551	459	87
Net Income Attributable to Northrim BanCorp, Inc.	$ 4,106	$ 5,335	$ 4,781	$ 3,561	$ 6,674	$ 3,707	$ 4,369	$ 2,658	$ 17,783	$ 17,408	$ 12,325
Earnings Per Share, Basic (USD per share)	$ 0.60	$ 0.78	$ 0.70	$ 0.52	$ 0.98	$ 0.54	$ 0.64	$ 0.41	$ 2.59	$ 2.57	$ 1.89
Earnings Per Share, Diluted (USD per share)	$ 0.59	$ 0.77	$ 0.69	$ 0.51	$ 0.97	$ 0.53	$ 0.63	$ 0.40	$ 2.56	$ 2.54	$ 1.87