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Summary of Significant Accounting Policies - Additional Information (Detail) | 6 Months Ended
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Jun. 30, 2012
Significant Accounting Policies [Line Items] |
Minimum likelihood of tax benefits being recognized upon ultimate settlement | 50.00%
Redemption Baskets |
Significant Accounting Policies [Line Items] |
Number of units per basket | 50,000
Prior to February 29, 2012 | Redemption Baskets |
Significant Accounting Policies [Line Items] |
Number of units per basket | 100,000
Maximum |
Significant Accounting Policies [Line Items] |
Cash equivalents maturity period | 6 months

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- Definition Cash Equivalents, Maturity Period + References No definition available. + Details
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- Definition Percentage Of Income Tax Examination Minimum Likelihood of Tax Benefits Being Realized Upon Settlement + References No definition available. + Details
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- Details
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