Fair Value Measurements (Narrative) (Details) - Weighted Average [Member] - Fair Value, Recurring [Member] - Significant Unobservable Inputs (Level 3) [Member]	Jun. 30, 2019	Dec. 31, 2018
Inventory Related Payables [Member]
Fair Value Measurements [Line Items]
Basis	29.60%	125.00%
Inventories Carried At Market [Member]
Fair Value Measurements [Line Items]
Basis	40.80%	18.50%