Note 7 - Deferred Rent - Summary of Deferred Rent (Details) (Parentheticals) $ in Thousands	Dec. 31, 2018 USD ($)
Current portion	$ 130

Current portion of amount of landlord-funded leasehold improvements after accumulated amortization.

No definition available.

Name:	blfs_LandlordfundedLeaseholdImprovementsNetCurrent
Namespace Prefix:	blfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant