Description of Business and Basis of Presentation (Details) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($)
Accounting Policies [Abstract]
Percentage of R&D staff on site at any time	50.00%
Accumulated deficit generated, since inception	$ (98,984)

Percentage of Research and Development Staff On-site at Any One Time

No definition available.

Name:	xcur_PercentageofResearchandDevelopmentStaffOnsiteatAnyOneTime
Namespace Prefix:	xcur_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration