Fair Value Measurements (Unobservable Inputs In Level 3 Valuations Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - Weighted Average [Member] - Significant Unobservable Inputs (Level 3) [Member] - Fair Value, Recurring [Member]	Jun. 30, 2019	Dec. 31, 2018
Inventory Related Payables [Member]
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Basis	29.60%	125.00%
Transportation cost	25.00%	39.40%
Commodity Derivative Contracts Losses [Member]
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Basis	22.60%	19.10%
Transportation cost	43.00%	35.10%
Inventories Carried At Market [Member]
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Basis	40.80%	18.50%
Transportation cost	31.50%	25.90%
Commodity Derivative Contracts Gains [Member]
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Basis	27.90%	21.60%
Transportation cost	32.30%	29.50%