Segment and Related Information, Additional information (Details) $ in Millions	9 Months Ended
Sep. 30, 2015 USD ($)
Additional information [Abstract]
Expired emission allowance credits	$ 35
Refining [Member]
Additional information [Abstract]
Expired emission allowance credits	$ 33

The expense charged against earnings for the periodic recognition of capitalized costs related to purchasing power, fuel, or emission credits. These items may be purchased in one accounting period but are deducted from earnings over time through amortization.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.3)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Name:	us-gaap_AmortizationOfPowerContractsEmissionCredits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration