Fund Investment Overview (Detail) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Schedule of Investments [Line Items]
Deposits with broker	$ 354,256,954	$ 454,297,809
Percentage of assets held by broker	100.00%	97.64%
Restricted investments	$ 18,351,850	$ 42,518,250
Percentage of holdings considered restricted	5.18%	9.36%

The amount due to the entity from other broker-dealers in the form of a deposit paid by the counterparty to demonstrate an intention to complete a purchase (good faith deposit) and also the amount due in the form of collateral deposited by the counterparty to cover the credit risk assumed by the entity (margin deposit).

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Paragraph 24

-IssueDate 2006-05-01

-Chapter 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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