Derivatives (Details 3) lb in Thousands, gal in Thousands, bu in Thousands, T in Thousands	Mar. 31, 2017 lb	Mar. 31, 2017 bu	Mar. 31, 2017 T	Mar. 31, 2017 gal	Dec. 31, 2016 lb	Dec. 31, 2016 bu	Dec. 31, 2016 T	Dec. 31, 2016 gal	Mar. 31, 2016 lb	Mar. 31, 2016 bu	Mar. 31, 2016 T	Mar. 31, 2016 gal
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	6,279	480,042	254	195,630	9,358	391,161	110	294,345	10,084	489,698	85	150,844
Non-exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	6,279	285,132	239	179,040	9,358	239,451	110	216,225	10,084	301,743	85	149,374
Non-exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	201,200	0	0	0	175,549	0	0	0	235,426	0	0
Non-exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	29,015	0	0	0	20,592	0	0	0	21,509	0	0
Non-exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	7,956	0	0	0	7,177	0	0	0	12,654	0	0
Non-exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	46,861	0	0	0	36,025	0	0	0	32,136	0	0
Non-exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	0	178,040	0	0	0	215,081	0	0	0	149,374
Non-exchange Traded | Corn Oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	6,279	0	0	0	9,358	0	0	0	3,850	0	0	0
Non-exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	100	239	1,000	0	108	110	1,144	6,234	18	85	0
Exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	194,910	15	16,590	0	151,710	0	78,120	0	187,955	0	1,470
Exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	104,790	0	0	0	63,225	0	0	0	129,465	0	0
Exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	47,605	0	0	0	39,005	0	0	0	34,315	0	0
Exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	40,855	0	0	0	45,360	0	0	0	20,950	0	0
Exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	1,660	0	0	0	4,120	0	0	0	3,225	0	0
Exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	0	16,590	0	0	0	78,120	0	0	0	1,470
Exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	15	0