Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interest
Beginning balance (in shares) at Dec. 31, 2014		6,854,000
Beginning balance, value at Dec. 31, 2014	$ 164,441	$ 6,854	$ 61,729	$ 95,493	$ 247	$ 118
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(5,126)			(5,126)
Stock-based compensation expense	608		608
Exercise of stock options and vesting of restricted stock units, net (in shares)		23,000
Exercise of stock options and vesting of restricted stock units, net	50	$ 23	27
Excess tax benefits from share-based payment arrangements	56		56
Distributions to noncontrolling interest	(490)					(490)
Other comprehensive income (loss), net of tax	(659)				(659)
Net income attributable to the noncontrolling interest	551					551
Net income attributable to Northrim BanCorp, Inc.	17,783			17,783
Ending balance (in shares) at Dec. 31, 2015		6,877,000
Ending balance, value at Dec. 31, 2015	177,214	$ 6,877	62,420	108,150	(412)	179
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(5,420)			(5,420)
Stock-based compensation expense	778		778
Exercise of stock options and vesting of restricted stock units, net (in shares)		21,000
Exercise of stock options and vesting of restricted stock units, net	$ (162)	$ 21	(183)
Treasury stock buy-back (in shares)	0
Excess tax benefits from share-based payment arrangements	$ (63)		(63)
Distributions to noncontrolling interest	(640)					(640)
Other comprehensive income (loss), net of tax	15				15
Net income attributable to the noncontrolling interest	579					579
Net income attributable to Northrim BanCorp, Inc.	$ 14,411			14,411
Ending balance (in shares) at Dec. 31, 2016	6,897,890	6,898,000
Ending balance, value at Dec. 31, 2016	$ 186,712	$ 6,898	62,952	117,141	(397)	118
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend declared	(5,970)			(5,970)
Stock-based compensation expense	665		665
Exercise of stock options and vesting of restricted stock units, net (in shares)		32,000
Exercise of stock options and vesting of restricted stock units, net	$ (243)	$ 32	(275)
Treasury stock buy-back (in shares)	(58,341)	(58,000)
Treasury stock buy-back	$ (1,607)	$ (58)	(1,549)
Distributions to noncontrolling interest	(445)					(445)
Other comprehensive income (loss), net of tax	212				212
Reclassification for remeasuring of deferred tax asset related to investment securities	0			85	(85)
Net income attributable to the noncontrolling interest	327					327
Net income attributable to Northrim BanCorp, Inc.	$ 13,151			13,151
Ending balance (in shares) at Dec. 31, 2017	6,871,963	6,872,000
Ending balance, value at Dec. 31, 2017	$ 192,802	$ 6,872	$ 61,793	$ 124,407	$ (270)	$ 0