Schedule of Investments (Parenthetical) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Schedule of Investments [Abstract]
Total U.S. Government and Agency Obligations, Cost	$ 149,828,083
Date of Repurchase Agreement with State Street Bank	Jun. 29, 2012
Repurchase price	13,600,984
Collateralized by U.S treasury notes	13,250,000
Treasury Notes , Interest rate	1.75%
Maturity date of Treasury Notes	May 31, 2016
Maturity value of Treasury Notes	13,874,976
Total Repurchase Agreements, Cost	13,600,973
Short-term investments, at cost	$ 163,429,056	$ 175,594,508