Summary of Significant Accounting Policies - Partnership's Maximum Exposure to Loss Relating to Non-Consolidated Vies (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Variable Interest Entity [Line Items]
Investments	$ (811.2)	$ (881.2)
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investments	385.2	398.2
Receivables	136.0	43.5
Maximum Exposure to Loss	$ 521.2	$ 441.7

For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Article 5

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

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-Name Accounting Standards Codification

-Topic 942

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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- Definition

Sum of the carrying amounts as of the balance sheet date of all investments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

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

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The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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