Derivatives (Details 4) lb in Thousands, gal in Thousands, bu in Thousands, T in Thousands	Dec. 31, 2016 bu	Dec. 31, 2016 lb	Dec. 31, 2016 gal	Dec. 31, 2016 T	Dec. 31, 2015 bu	Dec. 31, 2015 lb	Dec. 31, 2015 gal	Dec. 31, 2015 T
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	391,161	9,358	294,345	110	424,761	11,532	140,340	116
Non-exchange traded:
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	239,451	9,358	216,225	110	269,631	11,532	138,660	116
Non-exchange traded: | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	175,549	0	0	0	227,248	0	0	0
Non-exchange traded: | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	20,592	0	0	0	13,357	0	0	0
Non-exchange traded: | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	7,177	0	0	0	13,710	0	0	0
Non-exchange traded: | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	36,025	0	0	0	15,019	0	0	0
Non-exchange traded: | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	215,081	0	0	0	138,660	0
Non-exchange traded: | Corn oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	9,358	0	0	0	11,532	0	0
Non-exchange traded: | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	108	0	1,144	110	297	0	0	116
Exchange traded:
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	151,710	0	78,120	0	155,130	0	1,680	0
Exchange traded: | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	63,225	0	0	0	106,260	0	0	0
Exchange traded: | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	39,005	0	0	0	17,255	0	0	0
Exchange traded: | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	45,360	0	0	0	28,135	0	0	0
Exchange traded: | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	4,120	0	0	0	3,480	0	0	0
Exchange traded: | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	78,120	0	0	0	840	0
Exchange traded: | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	0	0	0	0	840	0