Segment Information - Schedule of Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015 Segment	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Number of segments	2
Total interest income	$ 14,386	$ 11,673
Interest expense on deposits, borrowings and junior subordinated debentures	754	440
Net Interest Income	13,632	11,233
Provision for loan losses	326	0
Other operating income	10,535	2,734
Other operating expense	18,461	9,967
Income before provision for income taxes	5,380	4,000
Provision for income taxes	1,747	1,297
Net income	3,633	2,703
Less: Net income attributable to the noncontrolling interest	72	45	459
Net income attributable to Northrim BanCorp	3,561	2,658	17,408
Total assets	1,447,984		1,449,349
Loans held for sale	61,873		43,866
Borrowings	22,569		26,304
Community Banking
Segment Reporting Information [Line Items]
Number of Stores	14
Total interest income	13,990	11,673
Interest expense on deposits, borrowings and junior subordinated debentures	474	440
Net Interest Income	13,516	11,233
Provision for loan losses	326	0
Other operating income	3,252	2,865
Other operating expense	13,324	9,967
Income before provision for income taxes	3,118	4,131
Provision for income taxes	813	1,351
Net income	2,305	2,780
Less: Net income attributable to the noncontrolling interest	72	45
Net income attributable to Northrim BanCorp	2,233	2,735
Total assets	1,369,167		1,391,862
Loans held for sale	0		0
Borrowings	2,153		2,164
Home Mortgage Lending
Segment Reporting Information [Line Items]
Total interest income	396	0
Interest expense on deposits, borrowings and junior subordinated debentures	280	0
Net Interest Income	116	0
Provision for loan losses	0	0
Other operating income	7,283	(131)
Other operating expense	5,137	0
Income before provision for income taxes	2,262	(131)
Provision for income taxes	934	(54)
Net income	1,328	(77)
Less: Net income attributable to the noncontrolling interest	0	0
Net income attributable to Northrim BanCorp	1,328	(77)
Total assets	78,817		57,487
Loans held for sale	61,873		43,866
Borrowings	$ 20,416		$ 24,140