Note 4 - Deferred Rent (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Amortization of Deferred Rent	$ 0	$ 32,000

The amount of amortization charged against earnings during the period for deferred rent.

No definition available.

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