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	9 Months Ended
	Sep. 30, 2021 MMBTU $ / gal $ / bbl $ / MMBTU gal bbl
Designated as hedges under accounting rules | Sell (Short) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls) | bbl	77
Weighted average contract price | $ / bbl	70.29
Designated as hedges under accounting rules | Buy (Long) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls) | bbl	0
Weighted average contract price | $ / bbl	0
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls) | bbl	320
Weighted average contract price | $ / bbl	71.26
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	69
Weighted average contract price | $ / MMBTU	5.83
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | NYM NYHBRULSD
Derivative [Line Items]
Contract volumes (bbls) | gal	43
Weighted average contract price | $ / gal	2.20
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Future | NYM RBOB Gas
Derivative [Line Items]
Contract volumes (bbls) | gal	97
Weighted average contract price | $ / gal	2.12
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Swaps | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	91
Weighted average contract price | $ / MMBTU	0.09
Not qualifying or not designated as hedges under accounting rules | Sell (Short) Contracts | Options | Crude Oil
Derivative [Line Items]
Contract volumes (bbls) | bbl	9
Weighted average premium received/paid | $ / bbl	1.20
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | Crude Oil
Derivative [Line Items]
Contract volumes (bbls) | bbl	116
Weighted average contract price | $ / bbl	71.64
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	186
Weighted average contract price | $ / MMBTU	4.42
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | NYM NYHBRULSD
Derivative [Line Items]
Contract volumes (bbls) | gal	0
Weighted average contract price | $ / gal	0
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Future | NYM RBOB Gas
Derivative [Line Items]
Contract volumes (bbls) | gal	0
Weighted average contract price | $ / gal	0
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Swaps | Natural Gas
Derivative [Line Items]
Contract volume (MMBTU) | MMBTU	0
Weighted average contract price | $ / MMBTU	0
Not qualifying or not designated as hedges under accounting rules | Buy (Long) Contracts | Options | Crude Oil
Derivative [Line Items]
Contract volumes (bbls) | bbl	6
Weighted average premium received/paid | $ / bbl	1.18