Net Earnings per Limited Partner Common Unit (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net earnings per limited partner common unit
Net earnings	$ 131.8	$ 128.4	$ 410.8	$ 378.2
Net earnings allocable to General Partner	(56.6)	(54.8)	(176.5)	(162.5)
Weighted average units outstanding	18.5	18.5	18.5	18.5
Net earnings per common unit (in dollars per unit)	$ 4.00	$ 3.91	$ 12.45	$ 11.46
Class B Common
Net earnings per limited partner common unit
Net earnings allocated	1.3	1.2	4.0	3.6
Common units
Net earnings per limited partner common unit
Net earnings allocated	$ 73.9	$ 72.4	$ 230.3	$ 212.1

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The portion of profit or loss for the period which is attributable to the parent.

+ References

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

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 51

-Paragraph 38

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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- Definition

Aggregate amount of net income allocated to general partners.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187171-122770

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section F

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Aggregate amount of net income allocated to limited partners.

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Net income (loss) allocated to each outstanding limited partnership unit.

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Weighted average number of limited partnership units outstanding determined by relating the portion of time within a reporting period that general partnership units have been outstanding to the total time in that period.

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