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Accounting policies (Details Textual) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 29, 2016
Accounting Policies [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax	$ 103,555	$ 65,147
Maximum [Member]
Accounting Policies [Line Items]
Percentage Of Bad Debts			1.00%	1.00%	1.00%
Aerex Industries Inc [Member]
Accounting Policies [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	51.00%					51.00%
Certificates of Deposit [Member]
Accounting Policies [Line Items]
Cash Equivalents, at Carrying Value	$ 13,600,000		$ 15,900,000
BELIZE
Accounting Policies [Line Items]
Deposits held in foreign bank	6,000,000
BAHAMAS
Accounting Policies [Line Items]
Deposits held in foreign bank	$ 11,900,000

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Amount of deposits held in foreign banks, as stated in equivalent United States dollars.

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The percentage representing the bad debts.

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895

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