Major Customers (Narrative) (Details)	12 Months Ended
Dec. 31, 2012 customer	Dec. 31, 2011 customer	Dec. 31, 2010 customer
Major Customers [Abstract]
Sales to largest customers (Percentage)	56.00%	53.00%	47.00%
Number of customers	10	10	10

Number of largest customers accounted for portion of revenue

No definition available.

Name:	bhe_NumberOfLargestCustomersAccountedForPortionOfRevenue
Namespace Prefix:	bhe_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration