Junior Subordinated Debentures (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2005	May. 31, 2003
Investment in unconsolidated trust	$ 51,774,000				$ 57,762,000				$ 51,774,000	$ 57,762,000
Junior subordinated debentures	18,558,000				18,558,000				18,558,000	18,558,000
Interest expense on deposits, borrowings and junior subordinated debentures	663,000	$ 706,000	$ 748,000	$ 754,000	$ 642,000	$ 487,000	$ 484,000	$ 440,000	2,871,000	2,053,000	$ 2,040,000
Northrim Capital Trust 1
Investment in unconsolidated trust													$ 8,000,000
Junior subordinated debentures	$ 8,200,000								$ 8,200,000
LIBOR period									90 days
Basis plus LIBOR									3.15%
Liquidation preference per capital security	$ 1,000								$ 1,000
Interest rate	3.51%								3.51%
Interest expense on deposits, borrowings and junior subordinated debentures									$ 289,000	274,000	278,000
Debt maturity date									May 15, 2033
Date debentures are redeemable									May 15, 2008
Northrim Capital Trust 2
Investment in unconsolidated trust												$ 10,000,000
Junior subordinated debentures	$ 10,300,000								$ 10,300,000
LIBOR period									90 days
Basis plus LIBOR									1.37%
Liquidation preference per capital security	$ 1,000								$ 1,000
Interest rate	1.88%								1.88%
Interest expense on deposits, borrowings and junior subordinated debentures									$ 174,000	$ 163,000	$ 167,000
Debt maturity date									Mar. 15, 2036
Date debentures are redeemable									Mar. 15, 2011