Derivatives (Outstanding Derivatives Entered Into to Hedge Inventory or Fixed Price Purchase Commitments) (Details) bbl in Thousands	12 Months Ended
Dec. 31, 2017 bbl $ / bbl
Sell (Short) Contracts \| Designated as Hedging Instrument [Member] \| Futures [Member] \| Crude Oil [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls) \| bbl	297
Weighted average contract price per bbl (in dollars per barrel) \| $ / bbl	57.70
Sell (Short) Contracts \| Not Designated As Hedging Instrument [Member] \| Futures [Member] \| Crude Oil [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls) \| bbl	223
Weighted average contract price per bbl (in dollars per barrel) \| $ / bbl	56.86
Sell (Short) Contracts \| Not Designated As Hedging Instrument [Member] \| Futures [Member] \| Fuel Oil Futures [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls) \| bbl	260
Weighted average contract price per bbl (in dollars per barrel) \| $ / bbl	55.01
Sell (Short) Contracts \| Not Designated As Hedging Instrument [Member] \| Options [Member] \| Crude Oil [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls) \| bbl	80
Weighted average premium received (in dollars per barrel) \| $ / bbl	0.85
Buy (Long) Contracts \| Designated as Hedging Instrument [Member] \| Futures [Member] \| Crude Oil [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls) \| bbl	0
Weighted average contract price per bbl (in dollars per barrel) \| $ / bbl	0.00
Buy (Long) Contracts \| Not Designated As Hedging Instrument [Member] \| Futures [Member] \| Crude Oil [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls) \| bbl	152
Weighted average contract price per bbl (in dollars per barrel) \| $ / bbl	57.30
Buy (Long) Contracts \| Not Designated As Hedging Instrument [Member] \| Futures [Member] \| Fuel Oil Futures [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls) \| bbl	20
Weighted average contract price per bbl (in dollars per barrel) \| $ / bbl	53.20
Buy (Long) Contracts \| Not Designated As Hedging Instrument [Member] \| Options [Member] \| Crude Oil [Member]
Derivative [Line Items]
Contract volumes (1,000 bbls) \| bbl	45
Weighted average premium received (in dollars per barrel) \| $ / bbl	0.24

- 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

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ 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

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

+ References

No definition available.

+ Details

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