Intangible Assets - Changes in Carrying Amount of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 773,048us-gaap_Goodwill	$ 778,708us-gaap_Goodwill
Acquisitions and purchase accounting adjustments	192,554	4,986
Translation impact	(22,228)us-gaap_GoodwillTranslationAdjustments	(10,646)us-gaap_GoodwillTranslationAdjustments
Goodwill, Ending Balance	943,374us-gaap_Goodwill	773,048us-gaap_Goodwill
Americas [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance		690,578
Reassignment of goodwill		(690,578)
EMEA [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance		70,328
Reassignment of goodwill		(70,328)
Asia Pacific [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance		17,802
Reassignment of goodwill		(17,802)
Broadcast Solutions [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	466,375
Reassignment of goodwill		473,029
Acquisitions and purchase accounting adjustments	119,918	4,986
Translation impact	(12,789)	(11,640)
Goodwill, Ending Balance	573,504	466,375
Enterprise Connectivity Solutions [Member]
Goodwill [Line Items]
Reassignment of goodwill		50,136
Goodwill, Ending Balance	50,136	50,136
Industrial Connectivity Solutions [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	187,975
Reassignment of goodwill		188,201
Acquisitions and purchase accounting adjustments	16,442
Translation impact	(4,364)	(226)
Goodwill, Ending Balance	200,053	187,975
Industrial IT Solutions [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	68,562
Reassignment of goodwill		67,342
Acquisitions and purchase accounting adjustments	56,194
Translation impact	(5,075)	1,220
Goodwill, Ending Balance	$ 119,681	$ 68,562

Business Acquisition Purchase Price Allocations Goodwill Amount

No definition available.

Name:	bdc_BusinessAcquisitionPurchasePriceAllocationsGoodwillAmount
Namespace Prefix:	bdc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

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

- Details

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

- Definition

Amount of transfers of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized among segments.

+ References

No definition available.

+ Details

Name:	us-gaap_GoodwillTransfers
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) from foreign currency translation adjustments of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillTranslationAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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