Commitments and Contingencies (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 jurisdictions	Feb. 29, 2012 lawsuit
Reclamation Surety Bonds
Surety bonds placed to secure the closure and reclamation obligations	$ 28.8
Purported class action and derivative lawsuits
Number of stockholder derivative lawsuits		7
Number of different jurisdictions in which lawsuits have been filed	3
Number of jurisdictions where defendants have filed a motion in each case seeking to consolidate derivative actions	1
Employees covered by collective bargaining agreement under facility | Workforce | Molycorp Silmet
Labor Contract
Number of employees	174
Concentration risk (as a percent)	30.00%
Employees covered by collective bargaining agreement under facility | Workforce | Molycorp Mountain Pass facility
Labor Contract
Number of employees	168
Concentration risk (as a percent)	57.00%