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Summary of significant accounting policies (Details 2)
 12 Months Ended
Jun. 30, 2018
Buildings And Facilities [Member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful life of property, plant and equipment Between 5 and 50 years
Machinery And Equipment [Member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful life of property, plant and equipment Between 3 and 24 years
Communication Networks [Member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful life of property, plant and equipment Between 4 and 20 years
Others [Member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Useful life of property, plant and equipment Between 3 and 25 years