Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value assets hierarchy levels transfers amount	$ 0	$ 0

Fair value assets hierarchy levels transfers amount.

No definition available.

Name:	ubx_FairValueAssetsHierarchyLevelsTransfersAmount
Namespace Prefix:	ubx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration