EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Computation of Basic Income per Share [Abstract]
Net income	$ 18.7	$ 47.2	$ 42.1	$ 133.7	$ 2.0	$ 31.8	$ 16.9	$ 14.1	$ 241.7	$ 64.8	$ 135.7
Basic									80.0	79.2	78.1
Basic net income per share (in dollars per share)	$ 0.23	$ 0.59	$ 0.53	$ 1.68	$ 0.03	$ 0.40	$ 0.21	$ 0.18	$ 3.02	$ 0.82	$ 1.74
Computation of Diluted Income per Share [Abstract]
Basic									80.0	79.2	78.1
Stock-based compensation (in shares)									0.8	0.7	0.2
Diluted									80.8	79.9	78.3
Diluted net income per share (in dollars per share)	$ 0.23	$ 0.58	$ 0.52	$ 1.66	$ 0.02	$ 0.40	$ 0.21	$ 0.18	$ 2.99	$ 0.81	$ 1.73
Antidilutive shares excluded from the computation of earnings per share (in shares)									0.9	1.3	3.2