Fair Value Disclosures (Details) (USD $)	Mar. 31, 2014		Dec. 31, 2013
Equity in broker trading accounts:
Net unrealized gain on open futures contracts	$ 12,066,277		$ 37,958,108
Net unrealized loss on open forward currency contracts	4,458,030		695,075
Recurring [Member]
Equity in broker trading accounts:
Net unrealized gain on open futures contracts	12,066,277	[1]	37,958,108	[1]
Net unrealized loss on open forward currency contracts	4,458,030	[1]	695,075	[1]
Cash and cash equivalents:
Money market fund	13,492,541		6,338,530
Total	511,922,044		618,539,012
Recurring [Member] | U.S. Treasury Securities [Member]
Cash and cash equivalents:
Total	64,041,413	[1]	88,102,079	[1]
Recurring [Member] | Commercial Paper [Member]
Cash and cash equivalents:
Total	65,614,198	[1]	65,153,483	[1]
Recurring [Member] | Corporate Notes [Member]
Cash and cash equivalents:
Total	322,764,643	[1]	377,666,684	[1]
Recurring [Member] | Certificates of Deposit [Member]
Cash and cash equivalents:
Total	29,484,942	[1]	42,625,053	[1]
Recurring [Member] | Level 1 [Member]
Equity in broker trading accounts:
Net unrealized gain on open futures contracts	12,066,277	[1]	37,958,108	[1]
Cash and cash equivalents:
Money market fund	13,492,541		6,338,530
Total	89,600,231		132,398,717
Recurring [Member] | Level 1 [Member] | U.S. Treasury Securities [Member]
Cash and cash equivalents:
Total	64,041,413	[1]	88,102,079	[1]
Recurring [Member] | Level 2 [Member]
Equity in broker trading accounts:
Net unrealized loss on open forward currency contracts	4,458,030	[1]	695,075	[1]
Cash and cash equivalents:
Total	422,321,813		486,140,295
Recurring [Member] | Level 2 [Member] | Commercial Paper [Member]
Cash and cash equivalents:
Total	65,614,198	[1]	65,153,483	[1]
Recurring [Member] | Level 2 [Member] | Corporate Notes [Member]
Cash and cash equivalents:
Total	322,764,643	[1]	377,666,684	[1]
Recurring [Member] | Level 2 [Member] | Certificates of Deposit [Member]
Cash and cash equivalents:
Total	$ 29,484,942	[1]	$ 42,625,053	[1]

[1] See the consolidated condensed schedule of investments for further description.