Note 8 - Commitments and Contingencies (Details Textual) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
Capital Expenditures Yet to Be Incurred	$ 1

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