Segment Information - Schedule of Segment Information (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) Segment bank	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of segments | Segment	2
Total interest income	$ 14,818	$ 14,386
Interest expense on deposits, borrowings and junior subordinated debentures	644	754
Net Interest Income	14,174	13,632
Provision for loan losses	703	326
Other operating income	9,105	10,535
Change in fair value, RML earn-out liability	130	1,502
Other operating expense	17,241	16,959
Income Before Provision for Income Taxes	5,205	5,380
Provision for income taxes	1,699	1,747
Net Income	3,506	3,633
Less: Net income attributable to the noncontrolling interest	130	72	$ 551
Net Income Attributable to Northrim BanCorp, Inc.	3,376	3,561	17,783
Total assets	1,500,199		1,499,492
Loans held for sale	$ 38,907		50,553
Community Banking
Segment Reporting Information [Line Items]
Number of Stores | bank	14
Total interest income	$ 14,448	13,990
Interest expense on deposits, borrowings and junior subordinated debentures	515	474
Net Interest Income	13,933	13,516
Provision for loan losses	703	326
Other operating income	3,409	3,229
Change in fair value, RML earn-out liability	130	1,502
Other operating expense	12,306	11,822
Income Before Provision for Income Taxes	4,203	3,095
Provision for income taxes	1,285	804
Net Income	2,918	2,291
Less: Net income attributable to the noncontrolling interest	130	72
Net Income Attributable to Northrim BanCorp, Inc.	2,788	2,219
Total assets	1,445,485		1,431,759
Loans held for sale	0		0
Home Mortgage Lending
Segment Reporting Information [Line Items]
Total interest income	370	396
Interest expense on deposits, borrowings and junior subordinated debentures	129	280
Net Interest Income	241	116
Provision for loan losses	0	0
Other operating income	5,696	7,306
Change in fair value, RML earn-out liability	0	0
Other operating expense	4,935	5,137
Income Before Provision for Income Taxes	1,002	2,285
Provision for income taxes	414	943
Net Income	588	1,342
Less: Net income attributable to the noncontrolling interest	0	0
Net Income Attributable to Northrim BanCorp, Inc.	588	$ 1,342
Total assets	54,714		67,733
Loans held for sale	$ 38,907		$ 50,553