Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Maximum [Member]	Mar. 28, 2012 Stillwater Canada, Inc. [Member]
Property, Plant and Equipment [Line Items]
Noncontrolling interest purchased by third party						25.00%
Letters of credit, expiration terms					1 year
Equity method investment, ownership percentage	20.00%
Property, plant, and equipment, useful life				3 years	7 years
Advertising costs	$ 10.8	$ 11.3	$ 2.1
Amount reclassified from property, plant and equipment, net to mineral properties and mine development, net for 2011		$ 268.3