Bank Credit Facility (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013
Bank Credit Facility (Textual)
Current borrowing base	$ 20.0
Maximum line of credit available under hedging arrangements	9.5
Line of credit facility, Maturity date	May 2017
Maximum borrowing base	50.0
Outstanding borrowings	12.6
Additional borrowing capacity available	$ 7.4
Effective borrowing rate (as a percent)	4.77%
Minimum [Member]
Bank Credit Facility (Textual)
Current ratio required to be maintained	1.0
Funded Debt Ratio required to be maintained	1.0
Maximum [Member]
Bank Credit Facility (Textual)
Current ratio required to be maintained	1.0
Funded Debt Ratio required to be maintained	4.25
Credit facility [Member]
Bank Credit Facility (Textual)
Variable interest rate basis	The portion of the loan based on an (Alternate Base Rate) is determined by the rate per annum equal to 1.5% plus the greatest of the following: (a) the Federal Funds Rate for such day plus one-half of one percentage point, (b) the Prime Rate for such day or (c) LIBOR for a one-month LIBOR Interest Period plus one percentage point.
Credit facility [Member] \| Alternate Base Rate [Member]
Bank Credit Facility (Textual)
Percentage points added to the reference rate	1.50%
Credit facility [Member] \| Alternate Base Rate [Member] \| Minimum [Member]
Bank Credit Facility (Textual)
Variable interest rate floor (as a percent)	4.50%
Credit facility [Member] \| LIBOR [Member] \| Minimum [Member]
Bank Credit Facility (Textual)
Percentage points added to the reference rate	2.50%
Credit facility [Member] \| LIBOR [Member] \| Maximum [Member]
Bank Credit Facility (Textual)
Percentage points added to the reference rate	3.25%

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Represents the ratio of current assets to current liabilities required to be maintained as per the terms of financial covenants.

+ References

No definition available.

+ Details

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- Definition

Represents the required funded debt ratio (the ratio of the outstanding balance of all interest bearing indebtedness to the sum of EBITDAX (net income plus interest expense, income taxes, depreciation, depletion, amortization, exploration and impairment expenses and other non-cash charges) required to be maintained as per the terms of financial covenants.

+ References

No definition available.

+ Details

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- Definition

Represents the floor for the reference rate used to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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- Definition

The maximum amount of borrowing capacity under a line of credit that is available as of the balance sheet date under hedging arrangements.

+ References

No definition available.

+ Details

Name:	crbo_LineOfCreditFacilityCapacityAvailableUnderHedgingArrangements
Namespace Prefix:	crbo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Amount borrowed under the credit facility as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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