Major Customers - Sales and Receivables (Detail) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2015
NGL Energy Ethanol [Member]
Revenue, Major Customer [Line Items]
Revenues	$ 88,579	$ 90,031
Receivable balance at period end	4,676		$ 3,272
Gavilon Distillers Grains [Member]
Revenue, Major Customer [Line Items]
Revenues	11,518	13,098
Receivable balance at period end	478		384
Dakotaland Feeds Distillers Grains [Member]
Revenue, Major Customer [Line Items]
Revenues	9,040	$ 9,302
Receivable balance at period end	$ 386		$ 206