Annual report pursuant to Section 13 and 15(d)

Summary of significant accounting policies - Property, Plant and Equipment (Details)

v3.19.1
Summary of significant accounting policies - Property, Plant and Equipment (Details)
12 Months Ended
Dec. 31, 2018
USD ($)
Property, Plant and Equipment [Line Items]  
Utility rebates applied to cost of construction $ 180,000
Minimum  
Property, Plant and Equipment [Line Items]  
Property, plant and equipment, estimated useful lives 3 years
Maximum  
Property, Plant and Equipment [Line Items]  
Property, plant and equipment, estimated useful lives 15 years