Related-Party Transactions (Details) $ in Thousands	4 Months Ended	6 Months Ended
	May 07, 2018 person	Jun. 30, 2018 USD ($) item	Jun. 30, 2017 USD ($)	May 31, 2016 item
Development Agreement
Inventory purchases | $		$ 305	$ 371
Medtronic
Board of Directors' Appointment
Number of person allowed for member of entities Board of Directors | person	1
Number of voting member before the Series F Preferred Stock purchase agreement				1
Number of voting member before the Series F Preferred Stock purchase agreement				2
Supply Agreement
Number of buy right of inventory upon termination of supply agreement		1
Right-of-First-Offer of the company
Period to negotiate exclusively with Medtronic on possible sale of business prior to negotiating with third party		90 days