Junior Subordinated Debentures (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May 31, 2003	Dec. 31, 2005
Investment in unconsolidated trust	$ 55,399				$ 40,666				$ 55,399	$ 40,666
Junior subordinated debentures	18,558				18,558				18,558	18,558
Interest expense on deposits, borrowings and junior subordinated debentures	642	487	484	440	497	502	511	530	2,053	2,040	2,505
Debt maturity date									Apr. 01, 2014
Northrim Capital Trust 1
Investment in unconsolidated trust												8,000
Junior subordinated debentures	8,200								8,200
LIBOR period									90 days
Basis plus LIBOR									3.15%
Liquidation preference per capital security	$ 1,000								$ 1,000
Interest rate	3.38%								3.38%
Interest expense on deposits, borrowings and junior subordinated debentures									274	278	292
Debt maturity date									May 15, 2033
Date debentures are redeemable									May 15, 2008
Northrim Capital Trust 2
Investment in unconsolidated trust													10,000
Junior subordinated debentures	10,300								10,300
LIBOR period									90 days
Basis plus LIBOR									1.37%
Liquidation preference per capital security	$ 1,000								$ 1,000
Interest rate	1.61%								1.61%
Interest expense on deposits, borrowings and junior subordinated debentures									$ 163	$ 167	$ 186
Debt maturity date									Mar. 15, 2036
Date debentures are redeemable									Mar. 15, 2011