Risk - Additional Information (Detail) |
9 Months Ended |
|---|---|
Sep. 30, 2017 | |
| Unusual Risk or Uncertainty [Line Items] | |
| Percentage of calculation on simple inverse correlation | 200.00% |
| Forward Agreements [Member] | |
| Unusual Risk or Uncertainty [Line Items] | |
| Exposure to swap agreements or forward contracts | 100.00% |
| Ultrashort Fund [Member] | |
| Unusual Risk or Uncertainty [Line Items] | |
| Leverage risk benchmark | 50% at any point in the day |