Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounts Receivable - Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 8,281	$ 11,503	$ 3,390
Charged to Costs and Expenses	2,517	2,561	1,184
Divestitures/ Acquisitions	(1)	40	9,845
Charge Offs	(1,336)	(803)	(1,867)
Recoveries	(1,046)	(4,353)	(889)
Currency Movement	(311)	(667)	(160)
Ending Balance	8,104	8,281	11,503
Inventories - Excess and Obsolete Allowances [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	22,531	31,823	21,317
Charged to Costs and Expenses	3,921	3,001	7,994
Divestitures/ Acquisitions	(706)	2,755	14,167
Charge Offs	0	(12,744)	(10,908)
Recoveries	(1,142)	(1,407)	(1,413)
Currency Movement	(43)	(897)	666
Ending Balance	24,561	22,531	31,823
Deferred Income Tax Asset - Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	117,071	157,317	10,165
Charged to Costs and Expenses	10,782	2,840	4,252
Divestitures/ Acquisitions	616	(14,425)	143,513
Charge Offs	(8,074)	(1,823)	0
Recoveries	(10,526)	(13,988)	(415)
Currency Movement	(5,098)	(12,850)	(198)
Ending Balance	$ 104,771	$ 117,071	$ 157,317

Valuation allowances and reserves reserves of businesses acquired and divestitures.

No definition available.

Name:	bdc_ValuationAllowancesAndReservesReservesOfBusinessesAcquiredAndDivestitures
Namespace Prefix:	bdc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of increase (decrease) in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from adjustments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

+ Details

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

- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

+ Details

Name:	us-gaap_ValuationAllowancesAndReservesBalance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase in the allowances and reserves, which consist of the valuation and qualifying accounts that are either netted against the cost of an asset or that reflect a liability established to represent expected future costs, from charges to costs and expenses.

+ References

+ Details

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

- Definition

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

+ References

+ Details

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

- Definition

+ References

+ Details

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

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_AllowanceForDoubtfulAccountsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_InventoryValuationReserveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: