Parent Company Information - Statements Of Income (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
Income
Interest income	$ 14,522	$ 14,860	$ 14,718	$ 14,818	$ 15,063	$ 15,388	$ 14,943	$ 14,386	$ 58,918	$ 59,780	$ 54,346
Other income	10,359	11,935	11,864	9,105	10,104	12,407	11,563	10,535	43,263	44,608	20,034
Expense
Interest expense	631	647	639	644	663	706	748	754	2,561	2,871	2,053
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
Benefit from 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 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
Northrim Bancorp, Inc.
Income
Interest income									369	116	197
Equity in undistributed earnings from subsidiaries									15,396	19,005	19,525
Other income									0	175	30
Total Income									15,765	19,296	19,752
Expense
Interest expense									534	463	451
Administrative and other expenses									2,382	2,191	3,243
Total Expense									2,916	2,654	3,694
Income Before Provision for Income Taxes									12,849	16,642	16,058
Benefit from income taxes									(1,562)	(1,141)	(1,350)
Net income attributable to Northrim BanCorp, Inc.									14,411	17,783	17,408
Northrim Bancorp, Inc. | Northrim Bank
Income
Equity in undistributed earnings from subsidiaries									15,301	18,865	19,358
Northrim Bancorp, Inc. | Northrim Investment Services Company
Income
Equity in undistributed earnings from subsidiaries									$ 95	$ 140	$ 167