Financial Highlights (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financial Highlights [Abstract]
Minimum rate of return	0.47%	0.60%	1.46%	2.20%
Maximum rate of return	0.69%	0.83%	1.92%	2.66%