Schedule of Volume of Activity Futures Contracts (Details) - Eurodollar Future - Contract	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivatives Fair Value [Line Items]
Number of contracts, Beginning of period	131,276	123,275	130,074	95,327
New positions opened	6,546	22,352	52,563	125,547
Early settlements	(5,220)	(12,016)	(32,369)	(83,444)
Settlements at maturity	(8,806)	(2,479)	(26,472)	(6,298)
Number of contracts, End of period	123,796	131,132	123,796	131,132