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v3.20.4

Stockholder Rights Plan (Details) - USD ($) $ / shares in Units, $ in Thousands |  | 12 Months Ended
--- | --- | ---
Mar. 27, 2018 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Equity [Abstract] |  |  |  |
Redemption price per share (in dollars per share) | $ 0.01 |  |  |
Preferred stock conversion | $ 400 | $ 0 | $ 0 | $ (411)

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- Definition Redemption Price Per Share Of Stockholders' Rights Agreement + References No definition available. + Details
Name: | bdc_RedemptionPricePerShareOfStockholdersRightsAgreement
Namespace Prefix: | bdc_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

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- Definition Redemption of Stockholders' Rights Agreement. + References No definition available. + Details
Name: | bdc_RedemptionofStockholdersRightsAgreements
Namespace Prefix: | bdc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_EquityAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration