Segment Reporting and Sales by Major Customer - Narrative (Details)	9 Months Ended
	Jan. 31, 2026 customer segment
Segment Reporting Information [Line Items]
Number of operating segments \| segment	2
Number of reportable segments \| segment	2
Customer Concentration Risk \| Revenue Benchmark \| The Five Aerospace Customers
Segment Reporting Information [Line Items]
Concentration risk, percentage	37.50%
Number of major customers \| customer	5
Customer Concentration Risk \| Revenue Benchmark \| Top Customer
Segment Reporting Information [Line Items]
Concentration risk, percentage	18.00%
Customer Concentration Risk \| Revenue Benchmark \| Next Top Four Customers \| Minimum
Segment Reporting Information [Line Items]
Concentration risk, percentage	2.00%
Customer Concentration Risk \| Revenue Benchmark \| Next Top Four Customers \| Maximum
Segment Reporting Information [Line Items]
Concentration risk, percentage	11.60%
Customer Concentration Risk \| Accounts Receivable \| Customer One
Segment Reporting Information [Line Items]
Concentration risk, percentage	22.20%
Number of major customers \| customer	1

BUTLER NATIONAL CORP 10-Q