Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Measurements

Schedule of assets and liabilities measured at fair value on a recurring basis

The following table sets forth financial assets and liabilities measured at fair value on a recurring basis in the consolidated balance sheet and the respective levels to which the fair value measurements are classified within the fair value hierarchy as of December 31 (in thousands):    

			Quoted Prices		Significant
			in Active		Other		Significant
			Markets for		Observable		Unobservable
			Identical Assets		Inputs		Inputs
	Total		(Level 1)		(Level 2)		(Level 3)
December 31, 2018
Short-term investments	$	228,783	$	-	$	228,783	$	-
Commodity futures – financial assets		4,558		-		4,558		-
Commodity futures – financial liabilities		3,890		-		3,890		-
December 31, 2017
Commodity futures – financial assets	$	2,790	$	-	$	2,790	$	-
Commodity futures – financial liabilities		10,506		-		10,506		-