Segment Information - Schedule of Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($) bank	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Segment bank	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of segments | Segment			2
Interest income	$ 14,860	$ 15,388	$ 44,396	$ 44,717
Interest expense	647	706	1,930	2,208
Net Interest Income	14,213	14,682	42,466	42,509
Provision for loan losses	652	676	1,555	1,378
Other operating income	11,935	12,407	32,904	34,505
Compensation expense - RML acquisition payments	3,250	780	4,067	2,869
Other operating expense	17,936	17,423	53,859	51,549
Income Before Provision for Income Taxes	4,310	8,210	15,889	21,218
Provision for income taxes	1,027	2,678	4,594	7,111
Net Income	3,283	5,532	11,295	14,107
Less: Net income attributable to the noncontrolling interest	188	197	474	431	$ 551
Net Income Attributable to Northrim BanCorp, Inc.	3,095	5,335	10,821	13,676	17,783
Total assets	1,540,120		1,540,120		1,499,492
Loans held for sale	$ 76,452		$ 76,452		50,553
Community Banking
Segment Reporting Information [Line Items]
Number of branches | bank	14		14
Interest income	$ 14,267	14,882	$ 42,962	43,227
Interest expense	366	457	1,299	1,302
Net Interest Income	13,901	14,425	41,663	41,925
Provision for loan losses	652	676	1,555	1,378
Other operating income	3,594	4,269	10,357	11,202
Compensation expense - RML acquisition payments	3,250	780	4,067	2,869
Other operating expense	11,649	11,853	36,459	35,106
Income Before Provision for Income Taxes	1,944	5,385	9,939	13,774
Provision for income taxes	50	1,513	2,140	4,038
Net Income	1,894	3,872	7,799	9,736
Less: Net income attributable to the noncontrolling interest	188	197	474	431
Net Income Attributable to Northrim BanCorp, Inc.	1,706	3,675	7,325	9,305
Total assets	1,440,441		1,440,441		1,431,759
Loans held for sale	0		0		0
Home Mortgage Lending
Segment Reporting Information [Line Items]
Interest income	593	506	1,434	1,490
Interest expense	281	249	631	906
Net Interest Income	312	257	803	584
Provision for loan losses	0	0	0	0
Other operating income	8,341	8,138	22,547	23,303
Compensation expense - RML acquisition payments	0	0	0	0
Other operating expense	6,287	5,570	17,400	16,443
Income Before Provision for Income Taxes	2,366	2,825	5,950	7,444
Provision for income taxes	977	1,165	2,454	3,073
Net Income	1,389	1,660	3,496	4,371
Less: Net income attributable to the noncontrolling interest	0	0	0	0
Net Income Attributable to Northrim BanCorp, Inc.	1,389	$ 1,660	3,496	$ 4,371
Total assets	99,679		99,679		67,733
Loans held for sale	$ 76,452		$ 76,452		$ 50,553