Fair Value Measurements (Details 1) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Assets and liabilities measured at fair value on a recurring basis
Restricted cash			$ 471
Commodity derivatives, net	[1]	$ 536	22,041
Provisionally priced contracts	[2]	(165,284)	(170,197)
Convertible preferred securities	[3]	7,388	3,294
Other assets and liabilities	[4]	8,461	6,861
Total		(148,899)	(137,530)
Level 1
Assets and liabilities measured at fair value on a recurring basis
Restricted cash			471
Commodity derivatives, net	[1]	18,603	29,872
Provisionally priced contracts	[2]	(98,190)	(105,321)
Convertible preferred securities	[3]	0	0
Other assets and liabilities	[4]	9,705	9,391
Total		(69,882)	(65,587)
Level 2
Assets and liabilities measured at fair value on a recurring basis
Restricted cash			0
Commodity derivatives, net	[1]	(18,067)	(7,831)
Provisionally priced contracts	[2]	(67,094)	(64,876)
Convertible preferred securities	[3]	0	0
Other assets and liabilities	[4]	(1,244)	(2,530)
Total		(86,405)	(75,237)
Level 3
Assets and liabilities measured at fair value on a recurring basis
Restricted cash			0
Commodity derivatives, net	[1]	0	0
Provisionally priced contracts	[2]	0	0
Convertible preferred securities	[3]	7,388	3,294
Other assets and liabilities	[4]	0	0
Total		$ 7,388	$ 3,294

[1] Includes associated cash posted/received as collateral

[2] Included in "Provisionally priced contracts" are those instruments based only on underlying futures values (Level 1) and delayed price contracts (Level 2)

[3] Recorded in “Other noncurrent assets” on the Company’s Consolidated Balance Sheets

[4] Included in other assets and liabilities are assets held by the Company to fund deferred compensation plans, ethanol risk management contracts, and foreign exchange derivative contracts (Level 1) and interest rate derivatives (Level 2