Summary of significant accounting policies (Details)	Jun. 07, 2018
Summary of significant accounting policies
Reverse stock split ratio	0.03625

Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

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