Derivatives (Volume of Contracts Outstanding) (Details) lb in Thousands, gal in Thousands, bu in Thousands, T in Thousands	Sep. 30, 2021 bu	Sep. 30, 2021 gal	Sep. 30, 2021 lb	Sep. 30, 2021 T	Dec. 31, 2020 bu	Dec. 31, 2020 gal	Dec. 31, 2020 lb	Dec. 31, 2020 T	Sep. 30, 2020 bu	Sep. 30, 2020 gal	Sep. 30, 2020 lb	Sep. 30, 2020 T
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	1,343,348	297,949	137,880	2,564	1,303,744	220,429	63,279	2,008	1,234,707	158,715	62,772	2,420
Non-exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	943,916	176,645	135,990	2,324	899,689	126,853	63,265	1,859	811,957	100,125	62,756	2,237
Non-exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	687,177	0	0	0	684,654	0	0	0	527,924	0	0	0
Non-exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	96,061	0	0	0	73,521	0	0	0	121,248	0	0	0
Non-exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	94,132	0	0	0	109,661	0	0	0	80,546	0	0	0
Non-exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	35,460	0	0	0	27,482	0	0	0	40,004	0	0	0
Non-exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	174,381	0	0	0	124,795	0	0	0	96,470	0	0
Non-exchange Traded | Corn oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	92,709	0	0	0	36,015	0	0	0	45,144	0
Non-exchange Traded | Soybean oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	41,322	0	0	0	26,510	0	0	0	17,262	0
Non-exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	31,086	2,264	1,959	2,324	4,371	2,058	740	1,859	42,235	3,655	350	2,237
Exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	399,432	121,304	1,890	240	404,055	93,576	14	149	422,750	58,590	16	183
Exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	236,395	0	0	0	267,792	0	0	0	250,445	0	0	0
Exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	60,660	0	0	0	53,730	0	0	0	62,785	0	0	0
Exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	101,087	0	0	0	80,733	0	0	0	108,805	0	0	0
Exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	1,290	0	0	0	1,800	0	0	0	715	0	0	0
Exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	96,894	0	0	0	73,584	0	0	0	19,488	0	0
Exchange Traded | Propane
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	24,402	0	0	0	17,094	0	0	0	31,962	0	0
Exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	8	1,890	240	0	2,898	14	149	0	7,140	16	183