Revenue - Subscription, License and Support Revenue (Details)	6 Months Ended
Jun. 30, 2018
Revenue recognition
Perpetual software licenses, estimated useful life	5 years

Perpetual Software Licenses Estimated Useful Life, Period

No definition available.

Name:	cblk_PerpetualSoftwareLicensesEstimatedUsefulLifePeriod
Namespace Prefix:	cblk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration