Basis of Presentation and Significant Accounting Policies - Components of Revenue and Cost of Revenue (Additional Information) (Details)	12 Months Ended
Dec. 31, 2018
Accounting Policies [Abstract]
Standard warranty period	1 year
Extended service renewal period	1 year

Revenue From Contract With Customer, Renewed Service Period

No definition available.

Name:	be_RevenueFromContractWithCustomerRenewedServicePeriod
Namespace Prefix:	be_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration