Description of Business and Basis of Presentation (Details) $ in Thousands	6 Months Ended
Jun. 30, 2020 USD ($) ft²
Accounting Policies [Abstract]
Lease area \| ft²	30,000
Accumulated deficit generated, since inception \| $	$ (103,295)

Retained Earnings (Accumulated Deficit), Inception to Date

No definition available.

Name:	xcur_RetainedEarningsAccumulatedDeficitInceptiontoDate
Namespace Prefix:	xcur_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant