Derivatives (Comodity Derivative Contracts Outstanding) (Details) lb in Thousands, gal in Thousands, bu in Thousands, T in Thousands	Dec. 31, 2019 lb	Dec. 31, 2019 bu	Dec. 31, 2019 T	Dec. 31, 2019 gal	Dec. 31, 2018 lb	Dec. 31, 2018 bu	Dec. 31, 2018 T	Dec. 31, 2018 gal
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	14,873	1,055,476	2,495	300,982	2,920	506,417	66	323,975
Non-exchange traded
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	14,873	724,330	2,263	120,448	2,920	313,612	66	246,863
Non-exchange traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	552,359	0	0	0	250,408	0	0
Non-exchange traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	34,912	0	0	0	22,463	0	0
Non-exchange traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	100,996	0	0	0	14,017	0	0
Non-exchange traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	24,700	0	0	0	26,230	0	0
Non-exchange traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	0	0	116,448	0	0	0	244,863
Non-exchange traded | Corn oil
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	14,568	0	0	0	2,920	0	0	0
Non-exchange traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	305	11,363	2,263	4,000	0	494	66	2,000
Exchange traded
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	331,146	232	180,534	0	192,805	0	77,112
Exchange traded | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	221,740	0	0	0	130,585	0	0
Exchange traded | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	39,145	0	0	0	26,985	0	0
Exchange traded | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	68,171	0	0	0	33,760	0	0
Exchange traded | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	2,090	0	0	0	1,475	0	0
Exchange traded | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	0	0	175,353	0	0	0	77,112
Exchange traded | Propane [Member]
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	0	0	5,166
Exchange traded | Other
Amounts of quantities outstanding included in commodity derivative contracts
Derivative, Nonmonetary Notional Amount	0	0	232	15