CONDENSED SCHEDULE OF INVESTMENTS (Unaudited) (USD $)	Jun. 30, 2011	Dec. 31, 2010
Investment Owned
Values	$ 3,145,326	$ 6,243,013
Values	(1,217,882)	(2,884,114)
Fixed Income Securities [Member]
Investment Owned
Values	1,169,987,017	1,024,388,662
% of net asset value (in hundredths)	96.59%	72.25%
Cost	1,169,558,238	1,024,136,134
Fixed Income Securities [Member] | Bank Deposits [Member]
Investment Owned
Values	200,797,983	47,567,480
% of net asset value (in hundredths)	16.57%	3.36%
Cost	200,750,957	47,545,000
Fixed Income Securities [Member] | Bank Deposits [Member] | Canada [Member] | Financials [Member]
Investment Owned
Values	81,208,700	14,557,945
% of net asset value (in hundredths)	6.70%	1.03%
Cost	81,200,717	14,545,000
Fixed Income Securities [Member] | Bank Deposits [Member] | Sweden [Member] | Financials [Member]
Investment Owned
Values	75,584,309
% of net asset value (in hundredths)	6.24%
Cost	75,550,000
Fixed Income Securities [Member] | Bank Deposits [Member] | United States [Member] | Financials [Member]
Investment Owned
Values	44,004,974	33,009,535
% of net asset value (in hundredths)	3.63%	2.33%
Cost	44,000,240	33,000,000
Fixed Income Securities [Member] | Commercial Paper [Member]
Investment Owned
Values	494,993,087	480,035,259
% of net asset value (in hundredths)	40.87%	33.84%
Cost	494,956,468	479,969,073
Fixed Income Securities [Member] | Commercial Paper [Member] | Australia [Member] | Financials [Member]
Investment Owned
Values		13,816,616
% of net asset value (in hundredths)		0.97%
Cost		13,810,957
Fixed Income Securities [Member] | Commercial Paper [Member] | Netherlands [Member] | Industrial [Member]
Investment Owned
Values	13,475,977	20,554,351
% of net asset value (in hundredths)	1.11%	1.45%
Cost	13,475,728	20,508,143
Fixed Income Securities [Member] | Commercial Paper [Member] | Panama [Member] | Consumer Discretionary [Member]
Investment Owned
Values	31,992,960	32,994,307
% of net asset value (in hundredths)	2.64%	2.33%
Cost	31,993,111	32,994,474
Fixed Income Securities [Member] | Commercial Paper [Member] | United Kingdom [Member] | Consumer Staples [Member]
Investment Owned
Values		11,532,293
% of net asset value (in hundredths)		0.81%
Cost		11,531,551
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member]
Investment Owned
Values	449,524,150	401,137,692
% of net asset value (in hundredths)	37.12%	28.28%
Cost	449,487,629	401,123,948
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Financials [Member]
Investment Owned
Values	132,166,698	42,144,129
% of net asset value (in hundredths)	10.91%	2.97%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Industrial [Member]
Investment Owned
Values	49,999,695	22,132,270
% of net asset value (in hundredths)	4.13%	1.56%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Consumer Discretionary [Member]
Investment Owned
Values		115,527,505
% of net asset value (in hundredths)		8.15%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Consumer Staples [Member]
Investment Owned
Values		6,683,703
% of net asset value (in hundredths)		0.47%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Energy [Member]
Investment Owned
Values	17,499,251	43,103,277
% of net asset value (in hundredths)	1.45%	3.04%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Health Care [Member]
Investment Owned
Values	79,999,664	56,326,259
% of net asset value (in hundredths)	6.61%	3.97%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Municipal [Member]
Investment Owned
Values		5,277,272
% of net asset value (in hundredths)		0.37%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Services [Member]
Investment Owned
Values		19,997,604
% of net asset value (in hundredths)		1.41%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Utilities [Member]
Investment Owned
Values		89,945,673
% of net asset value (in hundredths)		6.34%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Materials [Member]
Investment Owned
Values	127,472,503
% of net asset value (in hundredths)	10.52%
Fixed Income Securities [Member] | Commercial Paper [Member] | United States [Member] | Technology [Member]
Investment Owned
Values	42,386,339
% of net asset value (in hundredths)	3.50%
Fixed Income Securities [Member] | Corporate Bonds [Member] | United States [Member]
Investment Owned
Values	128,264,999
% of net asset value (in hundredths)	10.59%
Cost	127,926,544
Fixed Income Securities [Member] | Corporate Bonds [Member] | United States [Member] | Financials [Member]
Investment Owned
Values	89,655,409	104,048,295
% of net asset value (in hundredths)	7.40%	7.34%
Cost		103,844,282
Fixed Income Securities [Member] | Corporate Bonds [Member] | United States [Member] | Health Care [Member]
Investment Owned
Values	38,609,590
% of net asset value (in hundredths)	3.19%
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member]
Investment Owned
Values	345,930,668	392,736,787
% of net asset value (in hundredths)	28.56%	27.71%
Cost	345,923,989	392,776,938
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | Federal Home Loan Mortgage Corporation (FHLMC) [Member]
Investment Owned
Values	46,755,540
% of net asset value (in hundredths)	3.86%
Maturity face value	46,800,000
Due date	Jul. 05, 2013
Interest rate	0.0075
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | Federal Home Loan Mortgage Corporation Tranche [Member]
Investment Owned
Values	32,218,601
% of net asset value (in hundredths)	2.66%
Maturity face value	32,281,000
Due date	Jul. 05, 2013
Interest rate	0.0065
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | Other U.S. Government Agency [Member]
Investment Owned
Values	36,958,225	94,000,068
% of net asset value (in hundredths)	3.05%	6.63%
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | U.S. Treasury Bills Due 08/04/2011 [Member]
Investment Owned
Values	119,999,433
% of net asset value (in hundredths)	9.91%
Maturity face value	120,000,000
Due date	Aug. 04, 2011
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | U.S. Treasury Bills Due 09/08/2011 [Member]
Investment Owned
Values	54,999,465
% of net asset value (in hundredths)	4.54%
Maturity face value	55,000,000
Due date	Sep. 08, 2011
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | U.S. Treasury Bills Due 07/07/2011 [Member]
Investment Owned
Values	54,999,404
% of net asset value (in hundredths)	4.54%
Maturity face value	55,000,000
Due date	Jul. 07, 2011
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | U.S. Treasury Bills Due 1/6/2011 [Member]
Investment Owned
Values		74,998,646
% of net asset value (in hundredths)		5.29%
Maturity face value		75,000,000
Due date		Jan. 06, 2011
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | U.S. Treasury Bills Due 1/6/2011 [Member]
Investment Owned
Values		29,999,528
% of net asset value (in hundredths)		2.12%
Maturity face value		30,000,000
Due date		Jan. 06, 2011
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | U.S. Treasury Bills Due 01/13/2011 [Member]
Investment Owned
Values		74,997,625
% of net asset value (in hundredths)		5.29%
Maturity face value		75,000,000
Due date		Jan. 13, 2011
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | Federal Home Loan Bank Due 10/18/2012 [Member]
Investment Owned
Values		19,363,140
% of net asset value (in hundredths)		1.37%
Maturity face value		19,400,000
Due date		Oct. 18, 2012
Interest rate		0.00625
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | Federal Home Loan Bank Due 04/18/2011 [Member]
Investment Owned
Values		30,041,550
% of net asset value (in hundredths)		2.12%
Maturity face value		30,000,000
Due date		Apr. 18, 2011
Interest rate		0.0070
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | Federal Home Loan Bank BD Due 12/09/2011 [Member]
Investment Owned
Values		24,988,175
% of net asset value (in hundredths)		1.76%
Maturity face value		25,000,000
Due date		Dec. 09, 2011
Interest rate		0.0040
Fixed Income Securities [Member] | Government And Agency Obligations [Member] | United States [Member] | Federal Home Loan Bank BD Due 02/28/2011 [Member]
Investment Owned
Values		44,348,055
% of net asset value (in hundredths)		3.13%
Maturity face value		44,320,000
Due date		Feb. 28, 2011
Interest rate		0.0100
Fixed Income Securities [Member] | Short Term Investment Funds [Member] | United States [Member]
Investment Owned
Values	280	841
% of net asset value (in hundredths)	0.00%	0.00%
Cost	280	841
Future [Member]
Investment Owned
Values	(24,401,595)	18,350,278
% of net asset value (in hundredths)	(2.01%)	1.28%
Future [Member] | Long Futures Contracts [Member]
Investment Owned
Values	(16,465,267)	24,572,948
% of net asset value (in hundredths)	(1.36%)	1.72%
Future [Member] | Long Futures Contracts [Member] | Agricultural [Member]
Investment Owned
Values	(2,113,808)	9,251,944
% of net asset value (in hundredths)	(0.17%)	0.65%
Future [Member] | Long Futures Contracts [Member] | Energy [Member]
Investment Owned
Values	543,316	3,035,710
% of net asset value (in hundredths)	0.04%	0.21%
Future [Member] | Long Futures Contracts [Member] | Metals [Member]
Investment Owned
Values	88,122	10,794,183
% of net asset value (in hundredths)	0.01%	0.76%
Future [Member] | Long Futures Contracts [Member] | Stock Indices [Member]
Investment Owned
Values	10,688,352	(306,791)
% of net asset value (in hundredths)	0.88%	(0.02%)
Future [Member] | Long Futures Contracts [Member] | Short-term Interest Rates [Member]
Investment Owned
Values	(5,930,026)	1,605,624
% of net asset value (in hundredths)	(0.49%)	0.11%
Future [Member] | Long Futures Contracts [Member] | Long-term Interest Rates [Member]
Investment Owned
Values	(19,741,223)	192,278
% of net asset value (in hundredths)	(1.63%)	0.01%
Future [Member] | Short Futures Contract [Member]
Investment Owned
Values	(7,936,328)	(6,222,670)
% of net asset value (in hundredths)	(0.65%)	(0.44%)
Future [Member] | Short Futures Contract [Member] | Agricultural [Member]
Investment Owned
Values	2,943,483	(72,440)
% of net asset value (in hundredths)	0.24%	(0.01%)
Future [Member] | Short Futures Contract [Member] | Energy [Member]
Investment Owned
Values	(1,300,590)	(1,087,850)
% of net asset value (in hundredths)	(0.10%)	(0.08%)
Future [Member] | Short Futures Contract [Member] | Metals [Member]
Investment Owned
Values	(6,531,964)	(2,444,287)
% of net asset value (in hundredths)	(0.54%)	(0.17%)
Future [Member] | Short Futures Contract [Member] | Stock Indices [Member]
Investment Owned
Values	(2,892,241)	243,953
% of net asset value (in hundredths)	(0.24%)	0.02%
Future [Member] | Short Futures Contract [Member] | Short-term Interest Rates [Member]
Investment Owned
Values	(155,016)	(33,297)
% of net asset value (in hundredths)	(0.01%)	0.00%
Future [Member] | Short Futures Contract [Member] | Long-term Interest Rates [Member]
Investment Owned
Values		(2,828,749)
% of net asset value (in hundredths)		(0.20%)
Forward Currency Contracts [Member]
Investment Owned
Values	(1,630,388)	22,181,636
% of net asset value (in hundredths)	(0.13%)	1.56%
Forward Currency Contracts [Member] | Various Long Forward Currency Contracts [Member]
Investment Owned
Values	48,055,978	114,487,860
% of net asset value (in hundredths)	3.97%	8.07%
Forward Currency Contracts [Member] | Various Short Forward Currency Contracts [Member]
Investment Owned
Values	(49,686,366)	(92,306,224)
% of net asset value (in hundredths)	(4.10%)	(6.51%)
Purchased Options Forward Currency Contract [Member] | Options Forward Currency Contracts [Member]
Investment Owned
Values	3,145,326	6,243,013
% of net asset value (in hundredths)	0.26%	0.44%
Premiums paid	2,412,812	4,537,333
Written Options Forward Currency Contract [Member] | Options Forward Currency Contracts [Member]
Investment Owned
Values	(1,217,882)	(2,884,114)
Premiums received	$ 1,215,146	$ 988,402
% of net asset value (in hundredths)	(0.10%)	(0.20%)