Inventory - Narrative (Details)	3 Months Ended
Jul. 31, 2026
Inventory Disclosure [Abstract]
Duration during which inventory if inactive taken as obsolete (Year)	5 years

Represents the duration during which inventory if inactive taken as obsolete.

No definition available.

Name:	buks_DurationDuringWhichInventoryIfInactiveTakenAsObsolete
Namespace Prefix:	buks_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration