Derivatives (Details 3)	Mar. 31, 2014 lb	Dec. 31, 2013 bu	Mar. 31, 2013 bu
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	20,790,000	409,780,000	469,822,000
Non-exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	278,697,000	243,530,000	102,000
Non-exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	274,762,000	0	0
Non-exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	29,332,000	0	0
Non-exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	11,485,000	0
Non-exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	8,562,000
Non-exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	0
Non-exchange Traded | Corn Oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	20,790,000	0	0
Non-exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	207,000	0	0
Exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	253,300,000	166,250,000	0
Exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	124,420,000	0
Exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	0
Exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	32,760,000
Exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	6,820,000	0
Exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	21,630,000	0