Financial Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Foreign currency transaction loss	$ (24.4)	$ 7.7
Number of derivative require collateral security	0	0
Collateral to secure the derivative liability positions	0.7
Forward pricing agreements	36.3	30.8
Fair value forward pricing agreements	35.3	35.6
Unrealized loss related to forward pricing agreements	(1.0)
Unrealized gain related to forward pricing agreements		4.8
Interest Rate Swaps [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Notional amount of interest rate derivatives	32.1
February 2013 [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Maturity date of outstanding interest rate swap	February 2013
February 2013 [Member] \| Interest Rate Swaps [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Fixed interest rate on interest rate swap	4.20%
April 2013 [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Maturity date of outstanding interest rate swap	April 2013
April 2013 [Member] \| Interest Rate Swaps [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Fixed interest rate on interest rate swap	4.58%
June 2013 [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Maturity date of outstanding interest rate swap	June 2013
June 2013 [Member] \| Interest Rate Swaps [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Fixed interest rate on interest rate swap	4.48%
August 2014 [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Maturity date of outstanding interest rate swap	August 2014
August 2014 [Member] \| Interest Rate Swaps [Member] \| Spanish Term Loan [Member]
Derivatives, Fair Value [Line Items]
Fixed interest rate on interest rate swap	1.54%
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Unrealized loss on derivatives	6.1	6.0
Gain (loss) on derivative instruments not designated as cash flow hedges		$ 6.8

Collateral to secure the derivative liability positions.

No definition available.

Name:	bgc_CollateralToSecureDerivativeLiabilityPositions
Namespace Prefix:	bgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair value forward pricing agreements.

+ References

No definition available.

+ Details

Name:	bgc_FairValueForwardPricingAgreements
Namespace Prefix:	bgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Forward pricing agreements.

+ References

No definition available.

+ Details

Name:	bgc_ForwardPricingAgreements
Namespace Prefix:	bgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Maturity date of outstanding interest rate swap.

+ References

No definition available.

+ Details

Name:	bgc_MaturityDateOfOutstandingInterestRateSwap
Namespace Prefix:	bgc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of derivative require collateral security.

+ References

No definition available.

+ Details

Name:	bgc_NumberOfDerivativeRequireCollateralSecurity
Namespace Prefix:	bgc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Unrealized gain (loss) related to forward pricing agreements.

+ References

No definition available.

+ Details

Name:	bgc_UnrealizedGainLossRelatedToForwardPricingAgreements
Namespace Prefix:	bgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Unrealized gain related to forward pricing agreements.

+ References

No definition available.

+ Details

Name:	bgc_UnrealizedGainsRelatedToForwardPricingAgreements
Namespace Prefix:	bgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

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

- Definition

The amount of net gains and losses recognized in income during the period on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments not designated as hedging instruments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (a),(c),(d),(e)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

-Subparagraph b

-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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5618551-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossRecognizedInIncomeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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

- Definition

The net realized foreign currency transaction gain (loss) (pretax) included in determining net income from transactions that were settled as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 52

-Paragraph 30

-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 830

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450189&loc=d3e30690-110894

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 830

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 830

-SubTopic 20

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6450189&loc=d3e30700-110894

+ Details

Name:	us-gaap_ForeignCurrencyTransactionGainLossRealized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Aggregate notional amount of all interest rate derivatives designated as hedging instruments in cash flow hedges. Notional amount refers to the monetary amount specified in the interest rate derivative contract.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

+ Details

Name:	us-gaap_NotionalAmountOfInterestRateCashFlowHedgeDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-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 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

+ Details

Name:	us-gaap_UnrealizedGainLossOnDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration