Note 9 - Leases (Details Textual)	3 Months Ended
Mar. 31, 2020
Minimum [Member]
Operating Lease, Remaining Lease Term (Year)	1 year
Maximum [Member]
Operating Lease, Remaining Lease Term (Year)	5 years 146 days

Remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

No definition available.

Name:	nrc_OperatingLeaseRemainingLeaseTerm
Namespace Prefix:	nrc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration