Sales (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	Jul. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Sales Revenue, Goods, Net [Abstract]
Revenues from by-product sales		$ 6.7	$ 6.7
Term of refining agreement	5 years
Period after which refining agreement may be terminated	4 years