Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Property plant and equipment, accumulated depreciation	$ 722,600,000	$ 642,100,000
Intangible assets accumulated amortization	24,400,000	21,600,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	37,500,000	37,500,000
Common stock, shares issued	26,477,258	26,288,998
Common stock, shares outstanding	26,477,258	26,288,998
Allowance for doubtful accounts	$ 18.8	$ 18.9