Derivatives (Details 4) lb in Thousands, gal in Thousands, bu in Thousands, T in Thousands	Dec. 31, 2015 bu	Dec. 31, 2015 gal	Dec. 31, 2015 lb	Dec. 31, 2015 T	Dec. 31, 2014 bu	Dec. 31, 2014 gal	Dec. 31, 2014 lb	Dec. 31, 2014 T
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	424,761	140,340	11,532	116	556,574	275,469	20,776	144
Non-exchange traded:
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	269,631	138,660	11,532	116	327,829	233,637	18,076	139
Non-exchange traded: | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	227,248	0	0	0	265,574	0	0	0
Non-exchange traded: | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	13,357	0	0	0	23,820	0	0	0
Non-exchange traded: | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	13,710	0	0	0	14,967	0	0	0
Non-exchange traded: | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	15,019	0	0	0	23,440	0	0	0
Non-exchange traded: | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	138,660	0	0	0	233,637	0	0
Non-exchange traded: | Corn oil
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	0	11,532	0	0	0	18,076	0
Non-exchange traded: | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	297	0	0	116	28	0	0	139
Exchange traded:
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	155,130	1,680	0	0	228,745	41,832	2,700	5
Exchange traded: | Corn
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	106,260	0	0	0	159,575	0	0	0
Exchange traded: | Soybeans
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	17,255	0	0	0	31,265	0	0	0
Exchange traded: | Wheat
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	28,135	0	0	0	30,360	0	0	0
Exchange traded: | Oats
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	3,480	0	0	0	7,545	0	0	0
Exchange traded: | Ethanol
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	840	0	0	0	41,832	0	0
Exchange traded: | Other
Amounts of quantities outstanding included in commodity derivative contracts
Nonmonetary notional amount	0	840	0	0	0	0	2,700	5