Note 4 - Assets Held for Rent (Details Textual) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Assets Held for Rent, Depreciation	$ 671,000	$ 174,000

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