Derivatives (Volume of Contracts Outstanding) (Details) lb in Thousands, gal in Thousands, bu in Thousands, T in Thousands	Mar. 31, 2021 bu	Mar. 31, 2021 gal	Mar. 31, 2021 lb	Mar. 31, 2021 T	Dec. 31, 2020 bu	Dec. 31, 2020 gal	Dec. 31, 2020 lb	Dec. 31, 2020 T	Mar. 31, 2020 bu	Mar. 31, 2020 gal	Mar. 31, 2020 lb	Mar. 31, 2020 T
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	1,375,001	312,361	74,457	2,123	1,303,744	220,429	63,279	2,008	1,021,217	172,922	6,571	2,223
Non-exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	973,587	202,066	72,023	1,859	899,689	126,853	63,265	1,859	757,422	104,752	6,571	2,010
Non-exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	745,248	0	0	0	684,654	0	0	0	555,782	0	0	0
Non-exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	64,698	0	0	0	73,521	0	0	0	33,950	0	0	0
Non-exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	110,930	0	0	0	109,661	0	0	0	92,374	0	0	0
Non-exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	48,066	0	0	0	27,482	0	0	0	56,582	0	0	0
Non-exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	200,232	0	0	0	124,795	0	0	0	103,252	0	0
Non-exchange Traded | Corn oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	43,010	0	0	0	36,015	0	0	0	6,275	0
Non-exchange Traded | Soybean oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	28,573	0	0	0	26,510	0
Non-exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	4,645	1,834	440	1,859	4,371	2,058	740	1,859	18,734	1,500	296	2,010
Exchange Traded
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	401,414	110,295	2,434	264	404,055	93,576	14	149	263,795	68,170	0	213
Exchange Traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	262,920	0	0	0	267,792	0	0	0	165,295	0	0	0
Exchange Traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	62,020	0	0	0	53,730	0	0	0	37,875	0	0	0
Exchange Traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	76,164	0	0	0	80,733	0	0	0	59,135	0	0	0
Exchange Traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	310	0	0	0	1,800	0	0	0	1,490	0	0	0
Exchange Traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	96,978	0	0	0	73,584	0	0	0	44,440	0	0
Exchange Traded | Propane
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	12,894	0	0	0	17,094	0	0	0	11,760	0	0
Exchange Traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	423	2,434	264	0	2,898	14	149	0	11,970	0	213