Sales (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Jul. 31, 2014	Mar. 31, 2016	Mar. 31, 2015
Sales Revenue, Goods, Net [Abstract]
Revenues from by-product sales		$ 5.1	$ 6.7
Term of refining agreement	5 years
Period after which refining agreement may be terminated	4 years
Customer Concentration Risk [Member] | Total revenues [Member] | Customer A [Member]
Revenue, Major Customer [Line Items]
Sales to significant customers (10% or more), percentage of total revenues		80.00%	74.00%