Represents the additional borrowing allowed on compliance with financial covenants under the credit facility.

No definition available.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Represents the expected term of the debt instrument, which is the period that any debt discount will be amortized.

+ References

No definition available.

+ Details

Name:	cbst_DebtInstrumentTerm
Namespace Prefix:	cbst_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The 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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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

- Details

Name:	us-gaap_LineOfCreditFacilityLineItems
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Data Type:	xbrli:stringItemType
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Period Type:	duration

- 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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

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

Reference 3: 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

DEBT (Details 2) (Senior secured revolving credit facility, USD $) In Millions, unless otherwise specified	1 Months Ended				1 Months Ended			1 Months Ended
	Nov. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 03, 2013 Maximum	Sep. 30, 2013 Eurodollar rate	Sep. 03, 2013 Eurodollar rate Minimum	Sep. 03, 2013 Eurodollar rate Maximum	Sep. 30, 2013 Base rate	Sep. 03, 2013 Base rate Minimum	Sep. 03, 2013 Base rate Maximum
Credit Facility
Maximum borrowing capacity under credit facility	$ 150.0
Term of credit facility	3 years
Additional borrowing allowed subject to pro forma compliance with financial covenants				150.0
Basis spread on variable rate (as a percent)						2.25%	3.00%		1.25%	2.00%
Outstanding credit facility		$ 0	$ 0
Variable rate basis					Eurodollar rate			Base rate