CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data	Sep. 30, 2011	Dec. 31, 2010
CONSOLIDATED BALANCE SHEETS
Property, plant and equipment, accumulated depreciation, depletion and amortization (in dollars)	$ 2,364.5	$ 2,152.5
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	71,885,052	71,267,185
Common stock, shares outstanding		71,267,185
Treasury stock, shares (in shares)	5,559,051	0