Parent Company Information - Statements Of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income
Interest income	$ 18,062	$ 17,837	$ 17,306	$ 16,878	$ 17,207	$ 16,580	$ 15,595	$ 14,795	$ 70,083	$ 64,177	$ 60,108
Gain (loss) on marketable equity securities									911	(625)	0
Other income	9,735	10,509	9,569	7,533	7,718	8,673	8,314	7,462	37,346	32,167	40,474
Expense
Interest expense	1,652	1,531	1,349	1,109	1,070	761	606	532	5,641	2,969	2,430
Income Before Provision for Income Taxes	5,680	9,566	5,407	5,472	5,755	6,393	6,997	4,930	26,125	24,075	23,799
Benefit from income taxes	1,100	2,028	1,146	1,160	907	1,129	1,167	868	5,434	4,071	10,321
Net income attributable to Northrim BanCorp, Inc.	$ 4,580	$ 7,538	$ 4,261	$ 4,312	$ 4,848	$ 5,264	$ 5,830	$ 4,062	20,691	20,004	13,151
Northrim Bancorp, Inc.
Income
Interest income									635	477	408
Gain (loss) on marketable equity securities									911	(625)	0
Other income									44	5	0
Total Income									22,488	20,911	14,585
Expense
Interest expense									389	389	516
Administrative and other expenses									2,168	2,524	2,242
Total Expense									2,557	2,913	2,758
Income Before Provision for Income Taxes									19,931	17,998	11,827
Benefit from income taxes									(760)	(2,006)	(1,324)
Net income attributable to Northrim BanCorp, Inc.									20,691	20,004	13,151
Northrim Bancorp, Inc. | Northrim Bank
Income
Equity in undistributed earnings from subsidiaries									20,680	20,888	14,055
Northrim Bancorp, Inc. | Northrim Investment Services Company
Income
Equity in undistributed earnings from subsidiaries									$ 218	$ 166	$ 122