Stockholders' deficit - Warrants Outstanding (Details) - $ / shares	6 Months Ended	12 Months Ended
Jun. 30, 2019	Dec. 31, 2018
Beginning balance, warrants	97,799,908	49,504,075
Beginning balance, warrants exercise price	$ 0.0910	$ 0.0690
Warrants Granted, shares	19,235,183	48,295,833
Warrants granted, price	$ 0.1188	$ 0.1130
Warrants Forfeited, shares	(300,000)
Warrants Forfeited, price	$ (0.0033)
Ending Balance, warrants	116,735,091	97,799,908
Ending Balance, warrants exercise price	$ 0.0954	$ 0.0910
Weighted Average Contractual Life, warrants	2 years 11 months 19 days

Exercise price per share or per unit of warrants or rights outstanding.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Number of warrants or rights outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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Net number of non-option equity instruments granted to participants.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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