Fair Value Accounting - Schedule of Information About Assets Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Short-term available-for-sale investments	$ 222
Restricted cash	3,941	$ 3,941
Mineral properties	2,123
Total assets recorded at fair value	6,286	3,941
Level 1 [Member]
Short-term available-for-sale investments	222
Restricted cash	$ 3,941	39,414
Mineral properties
Total assets recorded at fair value	$ 4,163	$ 3,941
Level 2 [Member]
Restricted cash
Mineral properties
Total assets recorded at fair value
Level 3 [Member]
Restricted cash
Mineral properties	$ 2,123
Total assets recorded at fair value	$ 2,123
Fair Value, Inputs, Level 2 [Member]
Restricted cash
Total assets recorded at fair value