Derivatives (Schedule of Outstanding Derivatives Entered Into to Hedge Inventory or Fixed Price Purchase Commitments) (Details) bbl in Thousands	3 Months Ended
Mar. 31, 2018 bbl $ / bbl $ / units
Designated as Hedging Instrument \| Sell (Short) Contracts \| Future \| Crude Oil
Derivative [Line Items]
Contract volumes (1,000 bbls)	243
Weighted average contract price per bbl \| $ / bbl	62.41
Designated as Hedging Instrument \| Buy (Long) Contracts \| Future \| Crude Oil
Derivative [Line Items]
Contract volumes (1,000 bbls)	0
Weighted average contract price per bbl \| $ / bbl	0.00
Not Designated As Hedging Instrument \| Sell (Short) Contracts \| Future \| Crude Oil
Derivative [Line Items]
Contract volumes (1,000 bbls)	283
Weighted average contract price per bbl \| $ / bbl	63.92
Not Designated As Hedging Instrument \| Sell (Short) Contracts \| Future \| Natural Gas
Derivative [Line Items]
Contract volumes (1,000 bbls)	35
Weighted average contract price per bbl \| $ / bbl	2.74
Not Designated As Hedging Instrument \| Sell (Short) Contracts \| Future \| Diesel Futures
Derivative [Line Items]
Contract volumes (1,000 bbls)	6
Weighted average contract price per bbl \| $ / bbl	1.94
Not Designated As Hedging Instrument \| Sell (Short) Contracts \| Future \| NYM RBOB Gas Futures
Derivative [Line Items]
Contract volumes (1,000 bbls)	24
Weighted average contract price per bbl \| $ / bbl	1.97
Not Designated As Hedging Instrument \| Sell (Short) Contracts \| Future \| Fuel Oil Futures
Derivative [Line Items]
Contract volumes (1,000 bbls)	397
Weighted average contract price per bbl \| $ / bbl	54.55
Not Designated As Hedging Instrument \| Sell (Short) Contracts \| Swap \| Natural Gas
Derivative [Line Items]
Contract volumes (1,000 bbls)	275
Weighted average contract price per bbl \| $ / bbl	0.61
Not Designated As Hedging Instrument \| Sell (Short) Contracts \| Options \| Crude Oil
Derivative [Line Items]
Contract volumes (1,000 bbls)	70
Weighted average premium received \| $ / bbl	1.16
Not Designated As Hedging Instrument \| Buy (Long) Contracts \| Future \| Crude Oil
Derivative [Line Items]
Contract volumes (1,000 bbls)	145
Weighted average contract price per bbl \| $ / bbl	64.68
Not Designated As Hedging Instrument \| Buy (Long) Contracts \| Future \| Natural Gas
Derivative [Line Items]
Contract volumes (1,000 bbls)	275
Weighted average contract price per bbl \| $ / bbl	2.83
Not Designated As Hedging Instrument \| Buy (Long) Contracts \| Future \| Diesel Futures
Derivative [Line Items]
Contract volumes (1,000 bbls)	0
Weighted average contract price per bbl \| $ / bbl	0.00
Not Designated As Hedging Instrument \| Buy (Long) Contracts \| Future \| NYM RBOB Gas Futures
Derivative [Line Items]
Contract volumes (1,000 bbls)	16
Weighted average contract price per bbl \| $ / bbl	1.94
Not Designated As Hedging Instrument \| Buy (Long) Contracts \| Future \| Fuel Oil Futures
Derivative [Line Items]
Contract volumes (1,000 bbls)	40
Weighted average contract price per bbl \| $ / bbl	54.03
Not Designated As Hedging Instrument \| Buy (Long) Contracts \| Swap \| Natural Gas
Derivative [Line Items]
Contract volumes (1,000 bbls)	0
Weighted average contract price per bbl \| $ / units	0.00
Not Designated As Hedging Instrument \| Buy (Long) Contracts \| Options \| Crude Oil
Derivative [Line Items]
Contract volumes (1,000 bbls)	20
Weighted average premium received \| $ / bbl	0.29

- Definition

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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- Definition

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+ References

No definition available.

+ Details

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- Definition

Specified interest rate, security price, commodity price, foreign exchange rate, index of prices or rates for a derivative contract but not the derivative contract itself.

+ References

No definition available.

+ Details

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- Definition

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+ References

No definition available.

+ Details

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