Acquisitions and Investments Acquisitions and Investments (Investments in Pipeline Companies) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	9 Months Ended		0 Months Ended
Jun. 30, 2014 North Dakota Pipeline	Jun. 30, 2014 North Dakota Pipeline	Jan. 02, 2016 North Dakota Pipeline Class A Units Scenario, Forecast	Jan. 02, 2016 North Dakota Pipeline Class A Units Scenario, Forecast Maximum	Mar. 04, 2014 Explorer Pipeline	Jun. 30, 2014 Explorer Pipeline
Schedule of Equity Method Investments [Line Items]
Cash paid to acquire equity method investments	$ 75	$ 99			$ 77
Equity method investments, ownership percentage	37.50%	37.50%	27.00%	30.00%		25.00%
Ownership percentage acquired					7.00%

Percentage of voting equity interests acquired at the acquisition date in the business combination.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

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The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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