Supplemental Financial Data - Oil and Gas Producing Activities (unaudited) (Details 3) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Costs Incurred, Acquisition of Oil and Gas Properties [Abstract]
Total acquisition costs	$ 3,464	$ 1	$ 1,946

Costs incurred, including capitalized costs and costs charged to expense, associated with the acquisition of gas and oil properties that have unproved reserves.

No definition available.

Name:	crbo_CostsIncurredAcquisitionOfUnprovedGasAndOilProperties
Namespace Prefix:	crbo_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration