Summary of Significant Accounting Policies (Details) (USD $) In Millions, except Share data	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2011
Cash Distributions [Abstract]
Subsequent Cash Distribution, Declaration Date	2011-07-29
Subsequent Cash Distribution, Amount	$ 35.8
Subsequent Cash Distribution, Distribution Declared (in dollars per unit)	$ 0.34
Subsequent Cash Distribution, Distribution Date	2011-08-18
Subsequent Cash Distribution, Date of Record	2011-08-08
Compensatory Unit Awards and Option Plans [Abstract]
Holding Units Purchased in Period (in holding units)	2,500,000	4,700,000
Dollar Amount Paid for Holding Units Acquired	51.0	100.8
Open-market purchases of Holding Units (in holding units)	2,500,000	4,600,000
Dollar Amount Paid for Open-Market Purchases of Holding Units	$ 51.3	$ 99.0
Restricted Holding Unit Awards to Employees (in holding units)	1,600,000	1,700,000
Unallocated Holding Units Remaining in Consolidated Rabbi Trust (in holding units)	4,000,000	4,000,000
Newly-Issued Holding Units [Member] \| Long Term Incentive Plan [Member]
Compensatory Unit Awards and Option Plans [Abstract]
Shares Authorized Under Incentive Plan (in holding units)	30,000,000	30,000,000
Shares Available For Grant Under Incentive Plan (in holding units)	27,000,000	27,000,000
Repurchased Holding Units [Member] \| Long Term Incentive Plan [Member]
Compensatory Unit Awards and Option Plans [Abstract]
Shares Authorized Under Incentive Plan (in holding units)	30,000,000	30,000,000
Shares Available For Grant Under Incentive Plan (in holding units)	19,400,000	19,400,000
Long Term Incentive Plan [Member]
Compensatory Unit Awards and Option Plans [Abstract]
Restricted Holding Unit Awards to Employees (in holding units)		13,600,000

The amount paid for holding units purchased on the open market for issuance to employees under the plan.

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The amount paid for all shares purchased for the issuance to employees under the plan.

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Holding units purchased during the period for issuance to employees under the plan.

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Number of common stock held in a trust that has been set up specifically to accumulate stock for the sole purpose of distribution to participating employees but not yet earned.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 93-6
-Paragraph 14
-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 718
-SubTopic 40
-Section 25
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=6418455&loc=d3e16701-113920

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The equity impact of cash distributions declared to a common shareholder or unit-holder by a LLC or LP.

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Date of record for distribution of cash, stock, or units to a member or limited partner of LLC or LP.

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Date of declaration for distribution of cash, stock, or units to a member or limited partner of LLC or LP.

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Date of distribution for distribution of cash, stock, or units to a member or limited partner of LLC or LP.

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Per-share or per-unit cash distributions declared to a common shareholder or unit-holder by an LLC or LP.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph a
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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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The number of shares newly issued during the reporting period under the plan.

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The number of shares purchased on the open market during the period for issuance to employees under the plan.

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