Schedule of Volume of Activity Futures Contracts (Details) (Eurodollar Future)	12 Months Ended
	Dec. 31, 2014 Contract	Dec. 31, 2013 Contract
Eurodollar Future
Derivatives Fair Value [Line Items]
Number of contracts, Beginning of period	95,327
New positions opened	136,610	125,860
Early settlements	(93,053)	(28,164)
Settlements at maturity	(8,810)	(2,369)
Number of contracts, End of period	130,074	95,327