Subsequent Event (Details) - Oxide Plant $ / shares in Units, shares in Millions, $ in Millions		6 Months Ended
	Aug. 02, 2017 USD ($) item $ / shares shares	Jun. 30, 2017 USD ($)
Subsequent Events
Expected lease proceeds		$ 4.7
Subsequent Event
Subsequent Events
Renewal term	2 years
Expected lease proceeds	$ 1.0
Gross proceeds from common stock sale	$ 1.0
Common stock issued (in shares) | shares	1.8
Sale price (in dollars per shares) | $ / shares	$ 0.55
Volume weighted average stock price period	30 days
Termination notice period	120 days
Number of rights of first refusal | item	1