Accounting policies (Details Textual) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Feb. 11, 2016
Accounting Policies [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax			$ 8,089	$ 73,635
Cash, Uninsured Amount			2,700,000
Impairment of goodwill			0	1,400,000
Accumulated Amortization of Other Deferred Costs	$ 2,000,000		$ 2,200,000	2,000,000
Equity Method Investment, Additional Information			The Company uses the equity method of accounting for investments in common stock where the Company holds 20% to 50​​​​​​​% of the voting stock of the investee and has significant influence over its operating and financial policies but does not meet the criteria for consolidation.
Criteria For Recognizing Investment At Cost			Investments where the Company does not exercise significant influence over the operating and financial policies of the investee and holds less than 20% of the voting stock are recorded at cost​​​​​​​.
Cash Equivalents, at Carrying Value	16,388,030		$ 9,419,179	16,388,030
Cash And Restricted Cash Equivalents Held In Foreign Bank			28,900,000
Goodwill	8,003,568		8,003,568	8,003,568
Amortization of Other Deferred Charges			179,353	179,353
Disposal Group, Including Discontinued Operation, Goodwill, Noncurrent	380,680		380,680	380,680
Cw Belize [Member]
Accounting Policies [Line Items]
Disposal Group, Including Discontinued Operation, Goodwill, Noncurrent	381,000		$ 381,000	381,000
Maximum [Member]
Accounting Policies [Line Items]
Percentage Of Bad Debts			1.00%
Aerex Industries Inc [Member]
Accounting Policies [Line Items]
Impairment of goodwill	1,400,000	$ 1,750,000
Business Acquisition, Percentage of Voting Interests Acquired			51.00%		51.00%
Goodwill	4,885,211	$ 6,285,211		4,885,211	$ 8,035,211
Certificates of Deposit [Member]
Accounting Policies [Line Items]
Cash Equivalents, at Carrying Value	15,900,000		$ 8,400,000	$ 15,900,000
BAHAMAS
Accounting Policies [Line Items]
Deposits held in foreign bank			$ 4,300,000
Retail [Member]
Accounting Policies [Line Items]
Estimated Fair Value Carrying Amount Exceeded Percentage			79.00%	121.00%
Goodwill	1,170,511		$ 1,170,511	$ 1,170,511
Bulk [Member]
Accounting Policies [Line Items]
Estimated Fair Value Carrying Amount Exceeded Percentage			62.00%	59.00%
Goodwill	1,947,846		$ 1,947,846	$ 1,947,846
Capitalized Engineering Labor and Materials Cost [Member]
Accounting Policies [Line Items]
Other Assets	3,500,000		$ 3,500,000	$ 3,500,000
Manufacturing Units [Member]
Accounting Policies [Line Items]
Estimated Fair Value Carrying Amount Exceeded Percentage			53.00%	12.00%
Goodwill	$ 4,885,211		$ 4,885,211	$ 4,885,211