Summary of Significant Accounting Policies - Capital Leased Assets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Capital Leased Assets [Line Items]
Capital Leased Assets, Accumulated Amortization	$ (49)	$ (48)
Capital Leased Assets, Net of Amortization	161	164
Office Building [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	61	61
Nitrogen Plant [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	83	83
Computer-Related Equipment [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	60	62
Gas Pipeline [Member]
Capital Leased Assets [Line Items]
Capital Leased Assets, Gross	$ 6	$ 6

Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services.

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- Details

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- Definition

The total gross amount less the charge for the use of the long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

+ Details

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- Definition

The total charge for the use of long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6455314&loc=d3e45014-112735

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 10

-Section 55

-Paragraph 40

-Subparagraph (Note 2)

-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

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