Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Cash flows from operating activities:
Net income (loss)	$ (15,574,687)	$ (14,926,213)	$ (8,427,716)	$ 974,460	$ (16,706,421)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Purchases of short-term investments			(632,368,697)	(1,059,885,820)
Proceeds from sales and maturities of short-term investments			643,736,671	1,053,519,063
Premiums paid for call options written			(177,052)	(448,520)
Premiums received for call options written			4,489,456	5,351,925
Amortization (Accretion)			796,826	439,244
(Increase) Decrease in:
Deposits with brokers			8,995,035	(7,681,048)
Interest receivable			496,959	(677,274)
Other assets			(23,906)	(29,517)
Increase (Decrease) in:
Accrued management fees			(32,955)	(2,782)
Other accrued expenses			(72,689)	(72,524)
Net realized (gain) loss from:
Short-term investments		(10,899)	652	(10,899)
Call options written	(1,659,694)	(2,963,912)	(4,236,174)	(5,357,510)	(10,035,572)
Change in net unrealized (appreciation) depreciation of:
Short-term investments	4,822	(10,559)	28,176	7,586	(4,506)
Futures contracts	(7,190,243)	9,779,337	(7,710,570)	22,956,284	23,776,469
Call options written	1,352,546	134,460	1,709,545	(2,364,079)	(2,741,582)
Net cash provided by (used in) operating activities			7,203,561	6,718,589
Cash flows from financing activities:
Cash paid for shares repurchased			(519,611)
Cash distributions to shareholders			(6,683,950)	(6,718,605)
Net cash provided by (used in) financing activities			(7,203,561)	(6,718,605)
Net increase (decrease) in cash			0	(16)
Cash - beginning of period			0	16	16
Cash - end of period	$ 0	$ 0	$ 0	$ 0	$ 0