Junior Subordinated Debentures (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2005	May 31, 2003
Investment in unconsolidated trust	$ 56,128				$ 51,774				$ 56,128	$ 51,774
Junior subordinated debentures	18,558				18,558				18,558	18,558
Interest expense on deposits, borrowings and junior subordinated debentures	631	$ 647	$ 639	$ 644	$ 663	$ 706	$ 748	$ 754	2,561	2,871	$ 2,053
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 (in USD per share)	$ 1,000								$ 1,000
Interest rate	4.06%								4.06%
Interest expense on deposits, borrowings and junior subordinated debentures									$ 319	289	274
Debt maturity date									May 15, 2033
Date debentures are redeemable									May 15, 2008
Northrim Statutory 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 (in USD per share)	$ 1,000								$ 1,000
Interest rate	2.33%								2.33%
Interest expense on deposits, borrowings and junior subordinated debentures									$ 215	$ 174	$ 163
Debt maturity date									Mar. 15, 2036
Date debentures are redeemable									Mar. 15, 2011