SUMMARY OF QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) (USD $) In Thousands, except Per 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
SUMMARY OF QUARTERLY FINANCIAL INFORMATION (UNAUDITED) [Abstract]
Revenues	$ 14,632		$ 10,844		$ 10,799		$ 10,996		$ 12,326		$ 10,651		$ 13,152		$ 13,023		$ 13,938		$ 13,309		$ 13,725		$ 11,747		$ 47,271		$ 49,152		$ 52,719
Operating income (loss)	1,958		18		(198)		143		38		(520)		700		1,285		1,864		1,568		1,380		674		1,921		1,503		5,486
Non-operating income (expense)	(316)		(346)		(360)		(352)		(425)		(417)		(331)		(337)		(390)		(179)		(92)		(86)		(1,374)		(1,510)		(747)
Net income (loss) attributable to Butler National Corporation	$ 965		$ (219)		$ (345)		$ (289)		$ 225		$ (755)		$ 114		$ 268		$ 765		$ 568		$ 459		$ 108		$ 112		$ (148)		$ 1,900
Basic Earnings (Loss) per 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 (Loss) per 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]

[1] Rounded to nearest hundredth.