Derivatives (Schedule of Outstanding Derivatives Entered Into to Hedge Inventory or Fixed Price Purchase Commitments) (Details) bbl in Thousands, MMBTU in Thousands	9 Months Ended
	Sep. 30, 2020 MMBTU $ / bbl $ / MMBTU $ / units bbl
Designated as hedges under accounting rules | Sell (Short) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	444
Weighted average contract price	38.55
Designated as hedges under accounting rules | Buy (Long) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	0
Weighted average contract price	0
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	495
Weighted average contract price	41.36
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	92
Weighted average contract price | $ / MMBTU	2.25
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | Fuel Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	15
Weighted average contract price	37.10
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Swap | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	274
Weighted average contract price	0.27
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Options | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	33
Weighted average premium received/paid	0.82
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	312
Weighted average contract price	42.97
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	318
Weighted average contract price | $ / MMBTU	2.48
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | Fuel Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	20
Weighted average contract price	37.05
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Swap | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	0
Weighted average contract price | $ / units	0
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Options | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	13
Weighted average premium received/paid	0.15