Fair Value Measurement (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets (liabilities) measured at fair value
Total, fair value	$ (27,139)	$ (7,551)
Level 1
Assets (liabilities) measured at fair value
Total, fair value	5,443	7,187
Level 2
Assets (liabilities) measured at fair value
Total, fair value	8,909	24,581
Level 3
Assets (liabilities) measured at fair value
Total, fair value	(41,491)	(39,319)
Commodity contract derivatives
Assets (liabilities) measured at fair value
Assets, fair value	2,319	14,696
Commodity contract derivatives | Level 1
Assets (liabilities) measured at fair value
Assets, fair value	441	6,885
Commodity contract derivatives | Level 2
Assets (liabilities) measured at fair value
Assets, fair value	1,878	7,811
Commodity contract derivatives | Level 3
Assets (liabilities) measured at fair value
Assets, fair value	0	0
Contingent consideration for acquisition | LS9, Inc.
Assets (liabilities) measured at fair value
Liabilities, fair value	(7,258)	(8,624)
Contingent consideration for acquisition | LS9, Inc. | Level 1
Assets (liabilities) measured at fair value
Liabilities, fair value	0	0
Contingent consideration for acquisition | LS9, Inc. | Level 2
Assets (liabilities) measured at fair value
Liabilities, fair value	0	0
Contingent consideration for acquisition | LS9, Inc. | Level 3
Assets (liabilities) measured at fair value
Liabilities, fair value	(7,258)	(8,624)
Contingent consideration for acquisition | Dynamic Fuels, LLC
Assets (liabilities) measured at fair value
Liabilities, fair value	(29,233)	(30,695)
Contingent consideration for acquisition | Dynamic Fuels, LLC | Level 1
Assets (liabilities) measured at fair value
Liabilities, fair value	0	0
Contingent consideration for acquisition | Dynamic Fuels, LLC | Level 2
Assets (liabilities) measured at fair value
Liabilities, fair value	0	0
Contingent consideration for acquisition | Dynamic Fuels, LLC | Level 3
Assets (liabilities) measured at fair value
Liabilities, fair value	(29,233)	(30,695)
Contingent consideration for acquisition | Imperium Renewables, Inc.
Assets (liabilities) measured at fair value
Liabilities, fair value	(5,000)
Contingent consideration for acquisition | Imperium Renewables, Inc. | Level 1
Assets (liabilities) measured at fair value
Liabilities, fair value	0
Contingent consideration for acquisition | Imperium Renewables, Inc. | Level 2
Assets (liabilities) measured at fair value
Liabilities, fair value	0
Contingent consideration for acquisition | Imperium Renewables, Inc. | Level 3
Assets (liabilities) measured at fair value
Liabilities, fair value	(5,000)
Money market funds
Assets (liabilities) measured at fair value
Assets, fair value	5,002	302
Money market funds | Level 1
Assets (liabilities) measured at fair value
Assets, fair value	5,002	302
Money market funds | Level 2
Assets (liabilities) measured at fair value
Assets, fair value	0	0
Money market funds | Level 3
Assets (liabilities) measured at fair value
Assets, fair value	0	0
Certificates of deposit
Assets (liabilities) measured at fair value
Assets, fair value		9,995
Certificates of deposit | Level 1
Assets (liabilities) measured at fair value
Assets, fair value		0
Certificates of deposit | Level 2
Assets (liabilities) measured at fair value
Assets, fair value		9,995
Certificates of deposit | Level 3
Assets (liabilities) measured at fair value
Assets, fair value		0
Commercial paper
Assets (liabilities) measured at fair value
Assets, fair value	2,998
Commercial paper | Level 1
Assets (liabilities) measured at fair value
Assets, fair value	0
Commercial paper | Level 2
Assets (liabilities) measured at fair value
Assets, fair value	2,998
Commercial paper | Level 3
Assets (liabilities) measured at fair value
Assets, fair value	0
Commercial notes/bonds
Assets (liabilities) measured at fair value
Assets, fair value	4,033	6,775
Commercial notes/bonds | Level 1
Assets (liabilities) measured at fair value
Assets, fair value	0	0
Commercial notes/bonds | Level 2
Assets (liabilities) measured at fair value
Assets, fair value	4,033	6,775
Commercial notes/bonds | Level 3
Assets (liabilities) measured at fair value
Assets, fair value	$ 0	$ 0