Junior Subordinated Debentures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 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	Dec. 31, 2012 Northrim Capital Trust 1 [Member]	Dec. 31, 2011 Northrim Capital Trust 1 [Member]	May 31, 2003 Northrim Capital Trust 1 [Member]	Dec. 31, 2012 Northrim Capital Trust 2 [Member]	Dec. 31, 2011 Northrim Capital Trust 2 [Member]	Dec. 31, 2005 Northrim Capital Trust 2 [Member]
Investment in unconsolidated trust	$ 34,889				$ 34,238				$ 34,889	$ 34,238				$ 8,000			$ 10,000
Junior subordinated debentures					18,558					18,558		8,200			10,300
LIBOR period												90 days			90 days
Basis plus 90-day LIBOR												3.15%			1.37%
Liquidation preference per capital security												$ 1			$ 1
Interest rate												3.46%			1.68%
Interest cost	$ 569	$ 611	$ 627	$ 698	$ 787	$ 876	$ 904	$ 977	$ 2,505	$ 3,544	$ 5,485	$ 292	$ 281		$ 186	$ 171
Debt maturity date									Apr. 01, 2014			May 15, 2033			Mar. 15, 2036
Date debentures are redeemable												May 15, 2008			Mar. 15, 2011