EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Computation of Basic Income per Share [Abstract]
Net income	$ 38.7	$ 133.7
Basic shares (in shares)	80.1	79.6
Basic net income per share (in dollars per share)	$ 0.48	$ 1.68
Computation of Diluted Income per Share [Abstract]
Basic shares (in shares)	80.1	79.6
Stock-based compensation (in shares)	0.8	0.8
Diluted shares (in shares)	80.9	80.4
Diluted net income per share (in dollars per share)	$ 0.48	$ 1.66
Antidilutive shares excluded from the computation of earnings per share (in shares)	0.8	1.3