Derivative Instruments And Hedging Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012 bbl	Sep. 30, 2012 bbl	Dec. 31, 2011
Total volume of oil units	3,400,000	3,400,000
Total Volume Of Gas Units	8,700,000,000	8,700,000,000
Term loans payable	$ 200	$ 200	$ 200
Ineffectiveness on oil & gas commodity derivative contracts	10.0	2.3
Oil And Natural Gas Commodity Contracts [Member]
Future amount to be re-classified to earnings		(6.6)
Interest Rate Contracts [Member]
Future amount to be re-classified to earnings		$ (0.3)

The difference between the book value and the sale price of agreements to purchase or sell mineral resources, energy, and agricultural products at some future point. This element refers to the gain (loss) included in earnings and not to the cash proceeds.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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=6943989&loc=d3e3602-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration