v2.4.0.6

Risk - Additional Information (Detail) | 3 Months Ended
--- | ---
Mar. 31, 2013
Unusual Risk or Uncertainty [Line Items] |
Percentage of calculation on simple inverse correlation | 200.00%
UltraShort Fund [Member] |
Unusual Risk or Uncertainty [Line Items] |
Leverage risk benchmark | 50% at any point in the day
Swap agreements or forward contracts [Member] |
Unusual Risk or Uncertainty [Line Items] |
Exposure to swap agreements or forward contracts | 100.00%

X
- Definition Percentage Of Calculation On Simple Inverse Correlation + References No definition available. + Details
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Namespace Prefix: | ck0001415311_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage Of Credit Exposure + References No definition available. + Details
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Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Risk Related To Changes In Benchmark Interest Rate + References No definition available. + Details
Name: | ck0001415311_RiskRelatedToChangesInBenchmarkInterestRate
Namespace Prefix: | ck0001415311_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_UnusualRiskOrUncertaintyLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration