Basis of Presentation and Principles of Consolidation (Details)	Sep. 29, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Maximum percent of ownership to exercise significant influence	20.00%

Equity Method Investment, Percentage of Ownership Used to Account for Investments, Maximum

No definition available.

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Namespace Prefix:	bgc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant