Disclosures About Fair Value of Financial Instruments (Details) Notional Amounts of Derivatives	Mar. 31, 2014 T		Dec. 31, 2013 T
Exchange Traded | Agricultural Commodities Futures | Short
Derivatives, Fair Value [Line Items]
Notional amount of nonmonetary derivative	(54,855)	[1]	(23,038)	[1]
Exchange Traded | Agricultural Commodities Futures | Long
Derivatives, Fair Value [Line Items]
Notional amount of nonmonetary derivative	31,708	[1]	34,380	[1]
Exchange Traded | Natural Gas Futures | Long
Derivatives, Fair Value [Line Items]
Notional amount of nonmonetary derivative	400,000	[1],[2]	460,000	[1],[2]
Non-Exchange Traded | Forwards | Short
Derivatives, Fair Value [Line Items]
Notional amount of nonmonetary derivative	(117,801)	[1]	(132,428)	[1]
Non-Exchange Traded | Forwards | Long
Derivatives, Fair Value [Line Items]
Notional amount of nonmonetary derivative	72,900	[1]	30,367	[1]
Non-Exchange Traded | Swaps | Long
Derivatives, Fair Value [Line Items]
Notional amount of nonmonetary derivative	15,000	[1]	75,000	[1]

[1] Exchange and non-exchange traded futures, forwards, and swaps are presented on a gross (short) and long position basis.

[2] Million Metric British Thermal Units.