Counterparty Risk (% Of Due from Brokers) (Details) |
Sep. 30, 2017 |
|---|---|
| J.P. Morgan Securities LLC [Member] | |
| Concentration Risk [Line Items] | |
| % of Total Due from Brokers | 23.00% |
| Morgan Stanley [Member] | |
| Concentration Risk [Line Items] | |
| % of Total Due from Brokers | 20.00% |
| BNP Paribas Securities Corp. [Member] | |
| Concentration Risk [Line Items] | |
| % of Total Due from Brokers | 19.00% |