Business Combinations - Pro Forma Information (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended				12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro Forma Revenue			$ 50,143		$ 42,597
Net income attributable to Northrim BanCorp	3,707	3,474	10,734		9,644		12,325
Earnings Per Share, Basic (USD per share)	$ 0.54	$ 0.53	$ 1.59		$ 1.48
Earnings Per Share, Diluted (USD per share)	$ 0.53	$ 0.53	$ 1.57		$ 1.46
Weighted Average Shares Outstanding, Basic (shares)	6,831,976	6,515,455	6,733,175		6,514,441
Weighted Average Shares Outstanding, Diluted (shares)	6,919,993	6,607,201	6,822,288		6,594,482
Pro Forma Information, Revenue Since Acquisition			0	[1]	(28)	[1]
Pro Forma Information, Net Income (Loss) since Acquisition, Adjustment			(181)	[2]	101	[2]
Pro Forma Revenue			52,238		50,037
Pro Forma Net Income (Loss)			9,271		10,026
Pro Forma Earnings Per Share, Basic (USD per share)			$ 1.38		$ 1.54
Pro Forma Earnings Per Share, Diluted (USD per share)			$ 1.36		$ 1.52
Alaska Pacific Bank
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Pro Forma, Interest Income	4,400		2,095	[3]	7,468	[3]
Pro Forma Information, Net Income (Loss) Since Acquisition			$ (1,282)	[3]	$ 281	[3]

[1] Amount of amortization/ accretion of the fair value adjustments on loans and certificates of deposit.

[2] Amount of amortization/accretion of the fair value adjustments on loans and certificates of deposit, bargain purchase gain, amortization of cored deposit intangible, and the change in the provision for income taxes.

[3] Alaska Pacific represents results from January 1 to March 31 for 2014 and represents results from January 1 to September 30 for 2013.