XML 66 R55.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Fair Value of Assets and Liabilities - Narrative (Details) | 9 Months Ended
--- | ---
Sep. 30, 2017
Fair Value Disclosures [Abstract] |
Duration of purchased receivables (less than) | 1 year

X
- Definition Duration Of Fair Value Purchased Receivables + References No definition available. + Details
Name: | nrim_DurationOfFairValuePurchasedReceivables
Namespace Prefix: | nrim_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_FairValueDisclosuresAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration