Fair Value Measurements (Narrative) (Details) - Weighted Average [Member] - Fair Value, Measurements, Recurring [Member] - Significant Unobservable Inputs (Level 3) [Member]	Sep. 30, 2017	Dec. 31, 2016
Inventory Related Payables [Member]
Fair Value Measurements [Line Items]
Basis	62.70%	67.10%
Inventories Carried At Market [Member]
Fair Value Measurements [Line Items]
Basis	16.20%	16.50%