Derivatives (Schedule of Outstanding Derivatives Entered Into to Hedge Inventory or Fixed Price Purchase Commitments) (Details) gal in Thousands, bbl in Thousands, MMBTU in Thousands	6 Months Ended
	Jun. 30, 2019 MMBTU $ / bbl $ / MMBTU $ / gal $ / units gal bbl
Designated as hedges under accounting rules | Sell (Short) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	56
Weighted average contract price	53.93
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	384
Weighted average contract price	55.62
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	138
Weighted average contract price | $ / MMBTU	2.44
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | NYM NYHBRULSD
Derivative [Line Items]
Contract volumes (bbls/gal) | gal	35
Weighted average contract price	1.97
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | NYM RBOB
Derivative [Line Items]
Contract volumes (bbls/gal) | gal	5
Weighted average contract price | $ / gal	1.75
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | Fuel Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	233
Weighted average contract price	56.34
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Swap | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	549
Weighted average contract price	0.45
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Options | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	65
Weighted average premium received/paid	1.10
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls/gal) | bbl	132
Weighted average contract price	61.38
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	637
Weighted average contract price | $ / MMBTU	2.75
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | NYM NYHBRULSD
Derivative [Line Items]
Contract volumes (bbls/gal) | gal	19
Weighted average contract price	1.87
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | NYM RBOB
Derivative [Line Items]
Contract volumes (bbls/gal) | gal	5
Weighted average contract price | $ / gal	1.73
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | Fuel 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 | 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	20
Weighted average premium received/paid	0.32