Segment Information (Details) $ in Millions	3 Months Ended	6 Months Ended
Jul. 01, 2016 USD ($)	Jul. 03, 2015 USD ($)	Jul. 01, 2016 USD ($) Segment	Jul. 03, 2015 USD ($)	Dec. 31, 2015 USD ($)
Number of operating segments \| Segment			4
Number of reportable segments \| Segment			4
Revenues from transactions with other operating segments of same entity	$ 990.0	$ 1,113.4	$ 1,964.0	$ 2,284.5
Segment Operating Income (Loss)	58.1	23.7	73.4	39.9
Assets	2,466.6		2,466.6		$ 2,454.6
Intersegment Eliminations [Member] \| North America [Member]
Revenues from transactions with other operating segments of same entity	9.1	10.8	23.7	17.8
Intersegment Eliminations [Member] \| Europe [Member]
Revenues from transactions with other operating segments of same entity	1.1	1.8	4.4	14.3
Intersegment Eliminations [Member] \| Latin America [Member]
Revenues from transactions with other operating segments of same entity	6.2	5.2	9.8	9.5
Operating Segments [Member] \| North America [Member]
Revenues from transactions with other operating segments of same entity	530.9	609.4	1,069.1	1,247.6
Segment Operating Income (Loss)	73.8	30.9	91.5	60.5
Assets	960.1		960.1		986.9
Operating Segments [Member] \| Europe [Member]
Revenues from transactions with other operating segments of same entity	229.5	250.9	451.4	512.7
Segment Operating Income (Loss)	(1.5)	(1.2)	6.2	4.7
Assets	705.0		705.0		632.0
Operating Segments [Member] \| Latin America [Member]
Revenues from transactions with other operating segments of same entity	168.2	188.8	323.2	394.1
Segment Operating Income (Loss)	0.4	(2.5)	(3.3)	(18.4)
Assets	504.7		504.7		480.8
Operating Segments [Member] \| Africa/Asia Pacific [Member]
Revenues from transactions with other operating segments of same entity	61.4	64.3	120.3	130.1
Segment Operating Income (Loss)	(14.6)	$ (3.5)	(21.0)	$ (6.9)
Assets	$ 296.8		$ 296.8		$ 354.9

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfOperatingSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

+ Details

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

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

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

- Details

Name:	us-gaap_ConsolidationItemsAxis=us-gaap_IntersegmentEliminationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_NorthAmericaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_EuropeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_LatinAmericaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=bgc_AfricaAsiaPacificMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: