CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data	Jun. 30, 2011	Dec. 31, 2010
CONDENSED CONSOLIDATED BALANCE SHEETS
Mineral interests, accumulated depletion (in dollars)	$ 67.9	$ 17.6
Property, plant and equipment, accumulated depletion (in dollars)	$ 527.3	$ 433.1
Common stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, Authorized shares	200,000,000	200,000,000
Common stock, Issued shares	62,370,998	53,136,977
Preferred stock, par value per share (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, Authorized shares	20,000,000	20,000,000
Preferred stock, issued shares	0	0