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, 2021	Dec. 31, 2020
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	16.20%	13.70%
Transportation cost	0.00%	0.00%
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	39.60%	0.70%
Transportation cost	3.00%	1.30%
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	30.20%	4.30%
Transportation cost	12.50%	10.60%
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	29.50%	28.30%
Transportation cost	3.30%	1.90%