Derivatives (Details 5)	Dec. 31, 2012 lb
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	59,082,000
Non-exchange traded:
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	76,099,000
Non-exchange traded: | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Non-exchange traded: | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	14,455,000
Non-exchange traded: | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Non-exchange traded: | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Non-exchange traded: | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Non-exchange traded: | Corn oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Non-exchange traded: | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	27,000
Exchange traded:
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	1,000
Exchange traded: | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Exchange traded: | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Exchange traded: | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Exchange traded: | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Exchange traded: | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Exchange traded: | Bean oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0
Exchange traded: | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	1,000