Note 7 - Deferred Rent (Details Textual) - USD ($)	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
Mar. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2018
Amortization of Deferred Rent	$ 32,000		$ 63,000	$ 95,000	$ 127,000

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