Segment Information - Schedule of Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($) bank	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) Segment bank	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of segments | Segment			2
Total interest income	$ 14,943	$ 13,895	$ 29,329	$ 25,568
Interest expense on deposits, borrowings and junior subordinated debentures	748	484	1,502	924
Net Interest Income	14,195	13,411	27,827	24,644
Provision (benefit) for loan losses	376	(1,136)	702	(1,136)
Other operating income	11,563	4,106	22,098	6,840
Other operating expense	17,753	11,620	36,214	21,588
Income before provision for income taxes	7,629	7,033	13,009	11,032
Provision for income taxes	2,686	2,569	4,433	3,866
Net income	4,943	4,464	8,576	7,166
Less: Net income attributable to the noncontrolling interest	162	95	234	139	$ 459
Net income attributable to Northrim BanCorp, Inc.	4,781	4,369	8,342	7,027	17,408
Total assets	1,500,331		1,500,331		1,449,349
Loans held for sale	73,593		73,593		43,866
Borrowings	$ 22,309		$ 22,309		26,304
Community Banking
Segment Reporting Information [Line Items]
Number of Stores | bank	14		14
Total interest income	$ 14,354	13,895	$ 28,344	25,568
Interest expense on deposits, borrowings and junior subordinated debentures	370	484	844	924
Net Interest Income	13,984	13,411	27,500	24,644
Provision (benefit) for loan losses	376	(1,136)	702	(1,136)
Other operating income	3,724	3,751	6,976	6,616
Other operating expense	12,017	11,620	25,341	21,588
Income before provision for income taxes	5,315	6,678	8,433	10,808
Provision for income taxes	1,730	2,423	2,543	3,774
Net income	3,585	4,255	5,890	7,034
Less: Net income attributable to the noncontrolling interest	162	95	234	139
Net income attributable to Northrim BanCorp, Inc.	3,423	4,160	5,656	6,895
Total assets	1,411,506		1,411,506		1,391,862
Loans held for sale	0		0		0
Borrowings	2,142		2,142		2,164
Home Mortgage Lending
Segment Reporting Information [Line Items]
Total interest income	589	0	985	0
Interest expense on deposits, borrowings and junior subordinated debentures	378	0	658	0
Net Interest Income	211	0	327	0
Provision (benefit) for loan losses	0	0	0	0
Other operating income	7,839	355	15,122	224
Other operating expense	5,736	0	10,873	0
Income before provision for income taxes	2,314	355	4,576	224
Provision for income taxes	956	146	1,890	92
Net income	1,358	209	2,686	132
Less: Net income attributable to the noncontrolling interest	0	0	0	0
Net income attributable to Northrim BanCorp, Inc.	1,358	$ 209	2,686	$ 132
Total assets	88,825		88,825		57,487
Loans held for sale	73,593		73,593		43,866
Borrowings	$ 20,167		$ 20,167		$ 24,140