Note 5 - Assets Held for Rent (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Assets Held for Rent, Depreciation	$ 184,000	$ 128,000

The amount of depreciation expenses recognized for assets held for rent.

No definition available.

Name:	blfs_AssetsHeldForRentDepreciation
Namespace Prefix:	blfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration