Parent Company Information - Statements Of Income (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
Condensed Income Statements, Captions [Line Items]
Interest income	$ 15,063	$ 15,388	$ 14,943	$ 14,386	$ 14,566	$ 14,212	$ 13,895	$ 11,673	$ 59,780	$ 54,346	$ 46,074
Other income	10,104	12,407	11,563	10,535	9,376	4,934	4,106	2,734	44,608	21,149	12,886
Interest expense	663	706	748	754	642	487	484	440	2,871	2,053	2,040
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 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
Northrim Bancorp, Inc.
Condensed Income Statements, Captions [Line Items]
Interest income									116	197	208
Other income									175	30	170
Total Income									19,296	19,752	14,060
Interest expense									463	451	459
Administrative and other expenses									2,191	3,243	2,387
Total Expense									2,654	3,694	2,846
Income Before Provision for Income Taxes									16,642	16,058	11,214
Provision for income taxes									(1,141)	(1,350)	(1,111)
Net Income Attributable to Northrim BanCorp, Inc.									17,783	17,408	12,325
Northrim Bank | Northrim Bancorp, Inc.
Condensed Income Statements, Captions [Line Items]
Net income from subsidiary									18,865	19,358	13,645
Northrim Investment Services Company | Northrim Bancorp, Inc.
Condensed Income Statements, Captions [Line Items]
Net income from subsidiary									$ 140	$ 167	$ 37