INDUSTRY SEGMENTATION AND SALES BY MAJOR CUSTOMER (Details) $ in Thousands		3 Months Ended								12 Months Ended
		Apr. 30, 2016 USD ($) Customer	Jan. 31, 2016 USD ($)	Oct. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Apr. 30, 2015 USD ($)	Jan. 31, 2015 USD ($)	Oct. 31, 2014 USD ($)	Jul. 31, 2014 USD ($)	Apr. 30, 2016 USD ($) Segment Customer	Apr. 30, 2015 USD ($)
INDUSTRY SEGMENTATION AND SALES BY MAJOR CUSTOMER [Abstract]
Number of primary activities | Segment										2
Segment Reporting Information [Line Items]
Total revenues		$ 11,925	$ 11,067	$ 10,106	$ 11,696	$ 11,836	$ 11,083	$ 11,752	$ 12,391	$ 44,794	$ 47,062
Depreciation and amortization										2,174	2,885
Operating income (loss)		418	442	(599)	361	(389)	535	367	806	622	1,319
Capital expenditures, net										1,816	3,682
Interest expense										(471)	(1,141)
Other income (expense)										21	16
Income (loss) before taxes										908	967
Income tax expense (benefit)										93	138
Net income (loss) attributable to Butler National Corporation		381	$ 102	$ (478)	$ 19	(322)	$ 68	$ 29	$ 252	24	27
Identifiable assets, net		$ 42,697				41,598				$ 42,697	41,598
Revenue, Major Customer [Line Items]
Professional Services										14.50%
Number of major customers | Customer		5								5
Top Customer [Member]
Revenue, Major Customer [Line Items]
Professional Services										6.00%
Next Top Four Customers [Member] | Minimum [Member]
Revenue, Major Customer [Line Items]
Professional Services										1.90%
Next Top Four Customers [Member] | Maximum [Member]
Revenue, Major Customer [Line Items]
Professional Services										2.70%
Professional Services [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues										$ 29,784	30,795
Depreciation and amortization										1,390	1,573
Operating income (loss)										1,597	1,794
Capital expenditures, net										242	420
Interest expense										0	0
Other income (expense)										0	0
Income (loss) before taxes										0	0
Income tax expense (benefit)										0	0
Net income (loss) attributable to Butler National Corporation										0	0
Identifiable assets, net		$ 22,462				21,650				22,462	21,650
Aerospace Products [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues										15,010	16,267
Depreciation and amortization										784	1,312
Operating income (loss)										(975)	(475)
Capital expenditures, net										1,574	3,262
Interest expense										0	0
Other income (expense)										0	0
Income (loss) before taxes										0	0
Income tax expense (benefit)										0	0
Net income (loss) attributable to Butler National Corporation										0	0
Identifiable assets, net		$ 20,235				$ 19,948				$ 20,235	$ 19,948
Modifications [Member]
Revenue, Major Customer [Line Items]
Professional Services	[1]
Management Services [Member]
Revenue, Major Customer [Line Items]
Professional Services	[1]

[1] Revenue represented less than 10% of consolidated revenue.