Quarterly Results of Operations (Unaudited) (Details) - USD ($)		3 Months Ended								12 Months Ended
	Aug. 01, 2014	Apr. 30, 2016	Jan. 30, 2016	Oct. 31, 2015	Aug. 01, 2015	Apr. 30, 2015	Jan. 31, 2015	Nov. 01, 2014	Aug. 02, 2014	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Selected Quarterly Financial Information
Revenue		$ 84,757,000	$ 67,560,000	$ 64,731,000	$ 47,050,000	$ 86,471,000	$ 68,397,000	$ 52,664,000	$ 51,866,000	$ 264,098,000	$ 259,398,000	$ 251,703,000
Gross margin		37,922,000	26,625,000	31,533,000	16,023,000	45,350,000	26,993,000	17,871,000	14,054,000	112,103,000	104,268,000	93,613,000
Net (loss) income		$ 5,364,000	$ 6,164,000	$ 4,419,000	$ (6,981,000)	$ 7,080,000	$ 2,325,000	$ (2,901,000)	$ (3,609,000)	$ 8,966,000	$ 2,895,000	$ 13,718,000
Net (loss) income per share-basic		$ 0.23	$ 0.27	$ 0.19	$ (0.30)	$ 0.31	$ 0.10	$ (0.13)	$ (0.16)	$ 0.39	$ 0.13	$ 0.61
Net (loss) income per share-diluted		$ 0.23	$ 0.27	$ 0.19	$ (0.30)	$ 0.31	$ 0.10	$ (0.13)	$ (0.16)	$ 0.39	$ 0.13	$ 0.60
Other than temporary impairment of available-for-sale securities										$ 2,186,000
Cost of Revenue										151,995,000	$ 155,130,000	$ 158,090,000
Government contract accounting reserve								$ 2,600,000
Out-of-Period Adjustments
Selected Quarterly Financial Information
Cost of Revenue			$ 89,000
CybAero | Other Expense
Selected Quarterly Financial Information
Other than temporary impairment of available-for-sale securities	$ 2,186,000
UAS
Selected Quarterly Financial Information
Revenue										233,738,000	220,950,000	208,810,000
Gross margin										101,529,000	92,717,000	80,818,000
Cost of Revenue										132,209,000	128,233,000	127,992,000
EES
Selected Quarterly Financial Information
Revenue										30,360,000	38,448,000	42,893,000
Gross margin										10,574,000	11,551,000	12,795,000
Cost of Revenue										$ 19,786,000	$ 26,897,000	$ 30,098,000