Asset impairment (Tables)
|12 Months Ended|
Dec. 31, 2017
|Asset Impairment Charges [Abstract]|
|Schedule of asset impairment||
Asset impairment consisted of the following for the years ended December 31, 2017, 2016 and 2015:
Schedule of tangible and intangible asset impairment charges [Table Text Block]
No definition available.