BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended																								12 Months Ended
	Apr. 30, 2014		Jan. 31, 2014		Oct. 31, 2013		Jul. 31, 2013		Apr. 30, 2013		Jan. 31, 2013		Oct. 31, 2012		Jul. 31, 2012		Apr. 30, 2012		Jan. 31, 2012		Oct. 31, 2011		Jul. 31, 2011		Apr. 30, 2014		Apr. 30, 2013		Apr. 30, 2012
Accounts receivable [Abstract]
Duration after which invoices are considered to be doubtful																									90 days
Allowance for doubtful accounts	$ 72								$ 51																$ 72		$ 51
Inventories [Abstract]
Duration during which inventory if inactive taken as obsolete																									3 years
Obsolete inventory	1,381								1,400																1,381		1,400
Supplemental Type Certificates [Abstract]
Direct labor	1,033								1,018																1,033		1,018
Direct materials	1,833								1,546																1,833		1,546
Consultant costs	1,922								1,922																1,922		1,922
Overhead	1,797								2,020																1,797		2,020
Supplemental Type Certificates capitalized, gross	6,585								6,506																6,585		6,506
Less-amortized costs	2,841								2,642																2,841		2,642
STC balance	3,744								3,864																3,744		3,864
Revenue Recognition [Abstract]
Period for payment due																									30 days
Warranty period, minimum																									90 days
Warranty period, maximum																									36 months
Beginning warranty reserve							0								0										0		0
Additions to warranty reserve																									0		0		0
Reductions to warranty reserve																									0		0		0
Earnings Per Share [Abstract]
Net income (loss) attributable to Butler National Corporation	965		(219)		(345)		(289)		225		(755)		114		268		765		568		459		108		112		(148)		1,900
Weighted average common shares outstanding (in shares)																									60,893,092		59,014,594		56,596,214
Dilutive effect of non-qualified stock option plans (in shares)																									0		0		0
Weighted average common shares outstanding, assuming dilution (in shares)																									60,893,092		59,014,594		56,596,214
Potential common shares if all options were exercised and shares issued (in shares)																									68,155,156		66,281,237		64,848,201
Basic earnings per common share (in dollars per share)	$ 0.02	[1]	$ 0	[1]	$ (0.01)	[1]	$ 0.00	[1]	$ 0.00		$ (0.01)		$ 0.00		$ 0.00		$ 0.01	[1]	$ 0.01	[1]	$ 0.01	[1]	$ 0.00	[1]	$ 0.00	[1]	$ 0.00		$ 0.03	[1]
Diluted earnings per common share (in dollars per share)	$ 0.02	[1]	$ (0.01)	[1]	$ (0.01)	[1]	$ 0.00	[1]	$ 0.00	[1]	$ (0.01)	[1]	$ 0.00	[1]	$ 0.00	[1]	$ 0.01	[1]	$ 0.01	[1]	$ 0.01	[1]	$ 0.00		$ 0.00	[1]	$ 0.00	[1]	$ 0.03	[1]
Cash and Cash Equivalents [Abstract]
Bank deposits that exceeded the federally insured limits	2,242																								2,242
Research and Development [Abstract]
Research and development expense																									1,765		1,755
Kansas Expanded Lottery Act Management Contract Privilege Fee [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Other assets intangible	5,500								5,500																5,500		5,500
Less amortized costs intangible	987								564																987		564
Other assets net intangible, net	4,513								4,936																4,513		4,936
Gaming Equipment [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset, useful life																									3 years
Finite-Lived Intangible Assets, Net [Abstract]
Other assets intangible	2,252								1,182																2,252		1,182
Less amortized costs intangible	948								148																948		148
Other assets net intangible, net	1,304								1,034																1,304		1,034
JET Autopilot Intellectual Property [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset, useful life																									15 years
Amortization as a percentage of gross sales (in hundredths)																									5.00%
Finite-Lived Intangible Assets, Net [Abstract]
Other assets intangible	1,417								1,417																1,417		1,417
Less amortized costs intangible	585								491																585		491
Other assets net intangible, net	$ 832								$ 926																$ 832		$ 926
Minimum [Member]
Property, Plant and Equipment [Line Items]
Useful lives of property																									3 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Useful lives of property																									39 years

[1] Rounded to nearest hundredth.