Annual report pursuant to Section 13 and 15(d)

Segment Information (Narrative) (Details)

v3.10.0.1
Segment Information (Narrative) (Details) - segment
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Concentration Risk [Line Items]      
Number of reportable operating segments 2    
Sales Revenue, Net [Member] | Glencore U.K. [Member]      
Concentration Risk [Line Items]      
Concentration risk, percentage 100.00% 100.00% 100.00%