Parent Company Information - Statements Of Income (Details) (USD $) In Thousands, 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
Condensed Income Statements, Captions [Line Items]
Interest income	$ 15,178	$ 14,212	$ 13,895	$ 11,673	$ 12,018	$ 11,524	$ 11,440	$ 11,092	$ 54,958	$ 46,074	$ 44,728
Other income	8,764	4,934	4,106	2,734	2,802	3,243	3,702	3,139	20,537	12,886	15,432
Interest expense	642	487	484	440	497	502	511	530	2,053	2,040	2,505
Income Before Provision for Income Taxes	8,795	5,549	6,703	3,658	3,621	4,974	5,240	3,854	24,703	17,689	19,614
Provision for income taxes	1,991	1,651	2,239	955	1,042	1,510	1,635	1,090	6,836	5,277	6,156
Net income attributable to Northrim Bancorp	6,674	3,707	4,369	2,658	2,681	3,474	3,496	2,674	17,408	12,325	12,946
Northrim Bancorp, Inc.
Condensed Income Statements, Captions [Line Items]
Interest income									197	208	198
Other income									30	170	209
Total Income									19,752	14,060	14,392
Interest expense									451	459	493
Administrative and other expenses									3,243	2,387	1,646
Total Expense									3,694	2,846	2,139
Income Before Provision for Income Taxes									16,058	11,214	12,253
Provision for income taxes									(1,350)	(1,111)	(693)
Net income attributable to Northrim Bancorp									17,408	12,325	12,946
Northrim Bank | Northrim Bancorp, Inc.
Condensed Income Statements, Captions [Line Items]
Net income from subsidiary									19,358	13,645	13,950
Northrim Investment Services Company | Northrim Bancorp, Inc.
Condensed Income Statements, Captions [Line Items]
Net income from subsidiary									$ 167	$ 37	$ 35