Goodwill And Other Intangible Assets (Summary Of Intangible Assets Subject To Amortization) (Details) - USD ($)	6 Months Ended	12 Months Ended
	Oct. 31, 2017	Apr. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 8,912,000	$ 8,912,000
Accumulated Amortization	4,918,840	4,698,765
Able [Member] | Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	375,000	375,000
Accumulated Amortization	375,000	375,000
Able [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,395,000	2,395,000
Accumulated Amortization	$ 2,395,000	$ 2,395,000
Spitfire [Member] | Non-Contractual Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period	9 years 6 months 29 days	10 years 29 days
Gross Carrying Amount	$ 4,690,000	$ 4,690,000
Accumulated Amortization	1,422,770	1,237,410
Spitfire [Member] | Backlog [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	22,000	22,000
Accumulated Amortization	$ 22,000	$ 22,000
Spitfire [Member] | Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period	14 years 6 months 29 days	15 years 29 days
Gross Carrying Amount	$ 980,000	$ 980,000
Accumulated Amortization	$ 265,395	$ 240,897
Spitfire [Member] | Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period	1 year 6 months 29 days	2 years 29 days
Gross Carrying Amount	$ 50,000	$ 50,000
Accumulated Amortization	38,675	$ 35,105
Spitfire [Member] | Patents [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Remaining Amortization Period		29 days
Gross Carrying Amount	400,000	$ 400,000
Accumulated Amortization	$ 400,000	$ 393,353