Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2015

Accounting Policies [Abstract]

Activity regarding the allowance for doubtful accounts

Activity regarding the allowance for doubtful accounts was as follows:

Balance, January 1, 2013	$	1,972
Amount charged to selling, general and administrative expenses	309
Charge-offs, net of recoveries	(157		)
Balance, December 31, 2013	2,124
Amount charged to selling, general and administrative expenses	1,453
Charge-offs, net of recoveries	(1,304		)
Balance, December 31, 2014	2,273
Amount charged to selling, general and administrative expenses	(803		)
Charge-offs, net of recoveries	(119		)
Balance, December 31, 2015	$	1,351

Estimated useful lives

Depreciation expense is computed on a straight-line method based upon estimated useful lives of the assets. Estimated useful lives are as follows:

Automobiles and trucks	5 years
Computers and office equipment	5 years
Office furniture and fixtures	7 years
Machinery and equipment	5-30 years
Leasehold improvements	the lesser of the lease term or 30 years
Buildings and improvements	30-40 years

Goodwill for Company's business segments

The following table summarizes goodwill for the Company’s reportable segments:

	Biomass-based Diesel			Services		Renewable Chemicals			Total
Beginning balance - January 1, 2014	$	68,784		$	16,080	$	—		$	84,864
Acquisitions	68,564			—		34,847			103,411
Ending balance - December 31, 2014	137,348			16,080		34,847			188,275
Finalization of purchase accounting	2,833			—		—			2,833
Impairment charge	$	(140,181	)	$	—	$	(34,847	)	(175,028		)
Ending balance - December 31, 2015	$	—		$	16,080	$	—		$	16,080

Concentration risk by customer

One customer represented slightly less than 10% of the total consolidated revenues of the Company for the year ended December 31, 2015. This customer accounted for more than 10% of the total consolidated revenues of the Company for the two years ended December 31, 2014 and 2013. All customer amounts disclosed in the table are related to biomass-based diesel sales:

	2015		2014		2013
Customer A	$	114,030	$	231,780	$	243,258