Accounts Receivable Sale Program (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Receivables [Abstract]
Maximum Limit Accounts Receivable Sale Program	$ 40.0
Trade Accounts Receivable Sold	40.0	$ 25.0
Amount Received From Trade Accounts Receivable Sold To Third Party	39.9	24.9
Loss on sale of accounts receivable resulting from discount	$ 0.1	$ 0.1

Amount received upon sale of trade accounts receivable to third party.

No definition available.

Name:	bhe_AmountReceivedFromTradeAccountsReceivableSoldToThirdParty
Namespace Prefix:	bhe_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Accounts receivable program with third party maximum amount at any time that can be sold.

+ References

No definition available.

+ Details

Name:	bhe_MaximumLimitAccountsReceivableSaleProgram
Namespace Prefix:	bhe_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of trade accounts receivable that have been sold to a third party.

+ References

No definition available.

+ Details

Name:	bhe_TradeAccountsReceivableSold
Namespace Prefix:	bhe_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Reflects the net positive or negative amount derived from subtracting from net proceeds of sale, the carrying amounts, net of allocated reserves, of accounts receivable transferred to a third party in a transaction that qualifies for sales treatment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=82924980&loc=d3e107425-111719

+ Details

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

- References

No definition available.

+ Details

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