Segment Information - Schedule of Segment Information (Details) - USD ($) $ 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
Segment Reporting Information [Line Items]
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
Interest expense on deposits, borrowings and junior subordinated debentures	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
Change in fair value of RML earn-out liability									4,094	0	0
Other operating expense									68,551	48,038
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
Total assets	1,499,492				1,449,349				1,499,492	1,449,349
Loans held for sale	50,553				43,866				50,553	43,866
Community Banking
Segment Reporting Information [Line Items]
Total interest income									57,729	54,204
Interest expense on deposits, borrowings and junior subordinated debentures									1,796	1,942
Net Interest Income									55,933	52,262
Provision for loan losses									1,754	(636)
Other operating income									14,995	17,869
Change in fair value of RML earn-out liability									4,094
Other operating expense									47,070	46,165
Income Before Provision for Income Taxes									18,010	24,602
Provision for income taxes									5,024	7,582
Net Income									12,986	17,020
Less: Net income attributable to the noncontrolling interest									551	459
Net Income Attributable to Northrim BanCorp, Inc.									12,435	16,561
Total assets	1,431,759				1,390,852				1,431,759	1,390,852
Loans held for sale	0				0				0	0
Home Mortgage Lending
Segment Reporting Information [Line Items]
Total interest income									2,051	142
Interest expense on deposits, borrowings and junior subordinated debentures									1,075	111
Net Interest Income									976	31
Provision for loan losses									0	0
Other operating income									29,613	3,280
Change in fair value of RML earn-out liability									0
Other operating expense									21,481	1,873
Income Before Provision for Income Taxes									9,108	1,438
Provision for income taxes									3,760	591
Net Income									5,348	847
Less: Net income attributable to the noncontrolling interest									0	0
Net Income Attributable to Northrim BanCorp, Inc.									5,348	847
Total assets	67,733				58,497				67,733	58,497
Loans held for sale	$ 50,553				$ 43,866				$ 50,553	$ 43,866