Fair Value Measurements (Unobservable Inputs In Level 3 Valuations Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Document Period End Date	Dec. 31, 2019
Assets [Member] | Weighted Average [Member] | Inventories Component [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Recurring [Member]
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Basis	28.20%	18.50%
Transportation cost	24.70%	25.90%
Assets [Member] | Weighted Average [Member] | Commodity Derivative Contracts [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Recurring [Member]
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Basis	16.00%	21.60%
Transportation cost	9.70%	29.50%
Liabilities [Member] | Weighted Average [Member] | Inventories Component [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Recurring [Member]
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Basis	14.70%	125.00%
Transportation cost	0.00%	39.40%
Liabilities [Member] | Weighted Average [Member] | Commodity Derivative Contracts [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Recurring [Member]
Unobservable inputs in Level 3 Valuations of Assets and Liabilities Measured at Fair Value on a Recurring Basis [Line Items]
Basis	20.20%	19.10%
Transportation cost	3.10%	35.10%