EARNINGS PER SHARE (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Computation of Basic Income per Share [Abstract]
Net income	$ 34.6	$ 28.7	$ 47.6	$ 38.7	$ 18.7	$ 47.2	$ 42.1	$ 133.7	$ 149.6	$ 241.7	$ 64.8
Basic shares									80.1	80.0	79.2
Basic net income per share (in dollars per share)	$ 0.43	$ 0.36	$ 0.59	$ 0.48	$ 0.23	$ 0.59	$ 0.53	$ 1.68	$ 1.87	$ 3.02	$ 0.82
Computation of Diluted Income per Share [Abstract]
Basic shares									80.1	80.0	79.2
Stock-based compensation (in shares)									0.9	0.8	0.7
Diluted									81.0	80.8	79.9
Diluted net income per share (in dollars per share)	$ 0.43	$ 0.35	$ 0.59	$ 0.48	$ 0.23	$ 0.58	$ 0.52	$ 1.66	$ 1.85	$ 2.99	$ 0.81
Antidilutive shares excluded from the computation of earnings per share (in shares)									1.0	0.9	1.3