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v3.10.0.1

Revenue (Narrative) (Details) | 9 Months Ended
--- | ---
Sep. 30, 2018 | Sep. 30, 2017
Transferred Over Time [Member] |  |
Disaggregation Of Revenue [Line Items] |  |
Percentage Of Revenue | 93.00% | 93.00%

X
- Definition Percentage, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise. + References No definition available. + Details
Name: | bhe_PercentageOfRevenue
Namespace Prefix: | bhe_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DisaggregationOfRevenueLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_TimingOfTransferOfGoodOrServiceAxis=us-gaap_TransferredOverTimeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |