XML 87 R75.htm IDEA: XBRL DOCUMENT v3.19.1
Fair Value Measurement - Statement Of Income Classification (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Fair Value Statement Of Income Classification [Line Items]      
Derivative gain (loss) $ 900   $ (100)
Sales      
Fair Value Statement Of Income Classification [Line Items]      
Derivative gain (loss) 1,837 $ 571  
Other Operating Income (Expense)      
Fair Value Statement Of Income Classification [Line Items]      
Gold and silver rounds/bullion gain $ 15 $ 16