Commitments and Contingencies - Operating Leases - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	May 31, 2019
Lessee, Lease, Description [Line Items]
Lease expense	$ 134
Lease expense		$ 68
Term of contract				5 years
Option to renew	true
Renewal term				5 years
Right-of-use assets and other	$ 150	$ 9	$ 126
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]			Operating lease, liability current
Operating lease, liability current	$ 22		$ 20
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term Debt and Lease Obligation Other Than Convertible Notes		nrbo:LongTermDebtAndLeaseObligationOtherThanConverti
Operating lease, liability noncurrent	$ 94		$ 106
Operating lease discount rate	10.00%
Weighted average remaining lease term	4 years 6 months
Non-cash expense related to Korea lease	$ 126
Operating lease cash payments	16
Korea
Lessee, Lease, Description [Line Items]
Non-cash expense related to Korea lease	10
Head Quarters in Boston Lease [Member]
Lessee, Lease, Description [Line Items]
Term of contract			1 year
Right-of-use assets and other	$ 0