SIGNIFICANT ACCOUNTING POLICIES - BASIC AND DILUTED EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Income
Net Income, Basic									$ 103.0	$ 70.8	$ 53.7
Net Income, Diluted									$ 103.0	$ 70.8	$ 53.7
Weighted Average Common Shares
Basic (in shares)									43.5	43.0	42.7
Effect of Dilutive Securities (in shares)									0.5	0.4	0.4
Diluted (in shares)									44.0	43.4	43.1
Per Common Share Amount, Basic
Net income (in dollars per share)	$ 0.61	$ 0.95	$ 0.23	$ 0.58	$ 0.65	$ 0.50	$ 0.42	$ 0.08	$ 2.37	$ 1.65	$ 1.26
Per Common Share Amount, Diluted
Net income (in dollars per share)	$ 0.60	$ 0.94	$ 0.23	$ 0.57	$ 0.63	$ 0.50	$ 0.42	$ 0.08	$ 2.34	$ 1.63	$ 1.25
Stock options
Earnings Per Share ("EPS")
Antidilutive securities excluded from computation of earnings per share (in shares)									0.1	0.1	0.1