Quarterly Results Of Operations (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Results Of Operations [Abstract]
Total interest income	$ 11,349	$ 11,204	$ 11,123	$ 11,052	$ 11,540	$ 11,230	$ 11,486	$ 11,652	$ 44,728	$ 45,908	$ 49,698
Total interest expense	569	611	627	698	787	876	904	977	2,505	3,544	5,485
Net Interest Income	10,780	10,593	10,496	10,354	10,753	10,354	10,582	10,675	42,223	42,364	44,213
Provision for loan losses	(300)	(1,437)	89	89	350	550	550	549	(1,559)	1,999	5,583
Other operating income	4,343	4,157	3,725	3,207	3,880	3,362	3,070	2,778	15,432	13,090	12,377
Other operating expense	10,555	9,992	9,295	9,758	9,411	9,429	8,589	9,326	39,600	36,755	37,624
Income Before Provision for Income Taxes	4,868	6,195	4,837	3,714	4,872	3,737	4,513	3,578	19,614	16,700	13,383
Provision for income taxes	1,588	1,991	1,551	1,026	1,516	1,125	1,198	1,034	6,156	4,873	3,918
Net Income	3,280	4,204	3,286	2,688	3,356	2,612	3,315	2,544	13,458	11,827	9,465
Less: Net income attributable to the noncontrolling interest	118	138	144	112	101	106	133	89	512	429	399
Net Income Attributable to Northrim BanCorp	$ 3,162	$ 4,066	$ 3,142	$ 2,576	$ 3,255	$ 2,506	$ 3,182	$ 2,455	$ 12,946	$ 11,398	$ 9,066
Earnings per share, basic	$ 0.49	$ 0.63	$ 0.49	$ 0.40	$ 0.50	$ 0.39	$ 0.49	$ 0.38	$ 2.00	$ 1.77	$ 1.42
Earnings per share, diluted	$ 0.48	$ 0.62	$ 0.48	$ 0.39	$ 0.50	$ 0.38	$ 0.49	$ 0.37	$ 1.97	$ 1.74	$ 1.40