Additional Balance Sheet Information (Details 1) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Reclamation liability
Balance at beginning of the period	$ 9.9	$ 9.3	$ 8.0	$ 7.5
Settlement of obligations	(1.3)		(0.5)
Liabilities incurred and accretion expense	1.8		1.0
Foreign currency	0.1
Balance at end of period	$ 9.9	$ 9.3	$ 8.0	$ 7.5