Note 8 - Commitments and Contingencies (Details Textual) $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($)
Capital Expenditures Yet to Be Incurred	$ 1.6

Capital expenditures yet to be incurred, but are expected to incur within the fiscal year.

No definition available.

Name:	nvtr_CapitalExpendituresYetToBeIncurred
Namespace Prefix:	nvtr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration