Fair Value Measurements and Disclosures, Investment Percentages (Details)	Dec. 31, 2013	Dec. 31, 2012
TT II, LLC [Member]
Ownership Interests [Line Items]
Percentage of investment in trading companies (in hundredths)	27.65%	34.90%
WNT I, LLC [Member]
Ownership Interests [Line Items]
Percentage of investment in trading companies (in hundredths)	16.95%	20.15%
Kaiser I, LLC [Member]
Ownership Interests [Line Items]
Percentage of investment in trading companies (in hundredths)	8.30%	9.10%
Rotella I, LLC [Member]
Ownership Interests [Line Items]
Percentage of investment in trading companies (in hundredths)	17.95%	9.65%
Augustus I, LLC [Member]
Ownership Interests [Line Items]
Percentage of investment in trading companies (in hundredths)	19.20%	6.95%
Boronia I, LLC [Member]
Ownership Interests [Line Items]
Percentage of investment in trading companies (in hundredths)	9.95%
GLC I, LLC [Member]
Ownership Interests [Line Items]
Percentage of investment in trading companies (in hundredths)		6.70%
Chesapeake I, LLC [Member]
Ownership Interests [Line Items]
Percentage of investment in trading companies (in hundredths)		12.55%