Derivatives (Details 3) lb in Thousands, gal in Thousands, bu in Thousands, T in Thousands	Jun. 30, 2016 lb	Jun. 30, 2016 bu	Jun. 30, 2016 T	Jun. 30, 2016 gal	Dec. 31, 2015 lb	Dec. 31, 2015 bu	Dec. 31, 2015 T	Dec. 31, 2015 gal	Jun. 30, 2015 lb	Jun. 30, 2015 bu	Jun. 30, 2015 T	Jun. 30, 2015 gal
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	13,800	559,552	128	167,004	11,532	424,761	116	140,340	6,394	495,159	118	165,409
Non-exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	13,800	338,707	128	130,464	11,532	269,631	116	138,660	6,394	296,974	118	139,789
Non-exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	242,269	0	0	0	227,248	0	0	0	233,812	0	0
Non-exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	52,599	0	0	0	13,357	0	0	0	29,823	0	0
Non-exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	13,100	0	0	0	13,710	0	0	0	8,809	0	0
Non-exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	30,722	0	0	0	15,019	0	0	0	24,180	0	0
Non-exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	0	130,464	0	0	0	138,660	0	0	0	139,789
Non-exchange Traded | Corn Oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	13,800	0	0	0	11,532	0	0	0	6,394	0	0	0
Non-exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	17	128	0	0	297	116	0	0	350	118	0
Exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	220,845	0	36,540	0	155,130	0	1,680	0	198,185	0	25,620
Exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	148,665	0	0	0	106,260	0	0	0	139,965	0	0
Exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	46,570	0	0	0	17,255	0	0	0	30,945	0	0
Exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	22,790	0	0	0	28,135	0	0	0	22,585	0	0
Exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	2,820	0	0	0	3,480	0	0	0	4,690	0	0
Exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	0	36,540	0	0	0	840	0	0	0	25,620
Exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	0	0	0	0	0	840	0	0	0	0