Leases - Components of lease expense, and lease assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Lease Cost:
Amortization of right-of-use assets (included in depreciation expense)	$ 194	$ 178
Interest on lease liabilities	92	118
Operating lease cost	3,794	4,141
Short-term lease cost	90	241
Variable lease cost	467	510
Total lease cost	4,636	5,188
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows used for finance lease	103	127
Operating cash flows used for operating leases	4,285	3,988
Financing cash flows used for finance lease	380	312
Right-of-use assets obtained in exchange for new operating lease liabilities	12,124	$ 4,183
Assets and Liabilities, Lessee [Abstract]
Finance lease right-of-use assets (included in other assets)	$ 2,254		$ 2,448
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsMember		us-gaap:OtherAssetsMember
Operating lease right-of-use assets	$ 88,915		$ 79,966
Finance lease liability, current (included in current installments of long-term debt)	$ 1,709		$ 1,661
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	bhe:LongTermDebtAndCapitalLeaseObligationsCurrentMember		bhe:LongTermDebtAndCapitalLeaseObligationsCurrentMember
Finance lease liability, noncurrent (included in long-term debt)	$ 2,403		$ 2,832
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	bhe:LongTermDebtAndCapitalLeaseObligationsMember		bhe:LongTermDebtAndCapitalLeaseObligationsMember
Operating lease liabilities, current (included in accrued liabilities)	$ 12,318		$ 11,516
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesMember		us-gaap:AccruedLiabilitiesMember
Operating lease liabilities, noncurrent	$ 79,659		$ 72,120
Weighted average remaining lease term – finance leases	2 years 9 months 18 days		3 years
Weighted average remaining lease term – operating leases	10 years 1 month 6 days		10 years
Weighted average discount rate – finance leases	9.00%		9.00%
Weighted average discount rate – operating leases	4.20%		4.40%