Schedules of Investments (Unaudited) (Tables)

9 Months Ended

Sep. 30, 2015

Schedule of Investments [Abstract]

Investment [Table Text Block]

September 30, 2015
Security Description	Face Amount		Fair Value
U.S. Treasury bills(a):
0.01% due 10/01/15	$	89,000,000	$	89,000,000
0.01% - 0.02% due 10/08/15		132,000,000		132,000,396
0.00%(b) - 0.01% due 10/15/15		49,000,000		49,000,980
0.03% due 10/22/15		18,000,000		18,000,180
0.01% - 0.04% due 10/29/15		100,000,000		100,001,200
0.00%(b) - 0.01% due 12/24/15		215,000,000		215,007,525
0.02% due 12/31/15		89,000,000		88,999,466
0.08% due 01/07/16		50,000,000		49,999,150
0.12% - 0.13% due 01/14/16		75,000,000		74,998,350
0.12% due 02/04/16		10,000,000		9,999,340
Total United States Treasury bills (Cost: $826,935,744)				827,006,587
Total Investments – 110.61%				827,006,587
Other Assets, Less Liabilities – (10.61)%				(79,305,386	)
Net Assets – 100.00%			$	747,701,201

December 31, 2014
Security Description	Face Amount		Fair Value
United States Treasury bills(a):
0.01% - 0.06% due 01/08/15	$	32,300,000	$	32,299,935
0.02% - 0.06% due 01/15/15		41,671,000		41,670,625
0.06% due 01/22/15		85,655,000		85,653,544
0.02% - 0.06% due 01/29/15		60,274,000		60,272,855
0.01% - 0.06% due 02/05/15		44,568,000		44,566,930
0.03% - 0.05% due 02/12/15		145,000,000		144,997,100
0.01% - 0.05% due 02/19/15		66,336,000		66,334,475
0.03% due 03/05/15		104,000,000		103,996,880
0.03% - 0.05% due 03/12/15		137,000,000		136,993,424
0.04% due 04/16/15		27,000,000		26,997,273
0.07% due 05/28/15		41,000,000		40,989,176
Total United States Treasury bills (Cost: $784,754,985)				784,772,217
Total Investments – 99.70%				784,772,217
Other Assets, Less Liabilities – 0.30%				2,347,549
Net Assets – 100%			$	787,119,766

Schedule of Derivative Instruments [Table Text Block]

Number of Contracts	Expiration Date	Current Notional Amount		Net Unrealized Depreciation
29,515	December 2015	$	744,087,908	$	(16,884,863	)

Number of Contracts	Expiration Date	Current Notional Amount		Net Unrealized Depreciation
25,010	March 2015	$	785,521,583	$	(69,368,696	)