FAIR VALUE - Items Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Total
Cash equivalents:
Derivative assets (Note 14)	$ 1.0	$ 3.9
Total assets	306.3	274.3
Liabilities:
Derivative liabilities (Note 14)	4.2	1.9
Total liabilities	39.8	36.3
Bank time deposits with original maturities of three months or less | Total
Cash equivalents:
Bank time deposits with original maturities of three months or less	269.9	236.4
Diversified investments associated with the Executive Stock Unit Program (ESUP) | Total
Cash equivalents:
Diversified investments associated with the Executive Stock Unit Program (ESUP)	35.4	34.0
Liabilities associated with the ESUP | Total
Liabilities:
Total liabilities	35.6	34.4
Level 1
Cash equivalents:
Derivative assets (Note 14)	0.0	0.0
Total assets	35.4	34.0
Liabilities:
Derivative liabilities (Note 14)	0.0	0.0
Total liabilities	35.6	34.4
Level 1 | Bank time deposits with original maturities of three months or less
Cash equivalents:
Bank time deposits with original maturities of three months or less	0.0	0.0
Level 1 | Diversified investments associated with the Executive Stock Unit Program (ESUP)
Cash equivalents:
Diversified investments associated with the Executive Stock Unit Program (ESUP)	35.4	34.0
Level 1 | Liabilities associated with the ESUP
Liabilities:
Total liabilities	35.6	34.4
Level 2
Cash equivalents:
Derivative assets (Note 14)	1.0	3.9
Total assets	270.9	240.3
Liabilities:
Derivative liabilities (Note 14)	4.2	1.9
Total liabilities	4.2	1.9
Level 2 | Bank time deposits with original maturities of three months or less
Cash equivalents:
Bank time deposits with original maturities of three months or less	269.9	236.4
Level 2 | Diversified investments associated with the Executive Stock Unit Program (ESUP)
Cash equivalents:
Diversified investments associated with the Executive Stock Unit Program (ESUP)	0.0	0.0
Level 2 | Liabilities associated with the ESUP
Liabilities:
Total liabilities	0.0	0.0
Level 3
Cash equivalents:
Derivative assets (Note 14)	0.0	0.0
Total assets	0.0	0.0
Liabilities:
Derivative liabilities (Note 14)	0.0	0.0
Total liabilities	0.0	0.0
Level 3 | Bank time deposits with original maturities of three months or less
Cash equivalents:
Bank time deposits with original maturities of three months or less	0.0	0.0
Level 3 | Diversified investments associated with the Executive Stock Unit Program (ESUP)
Cash equivalents:
Diversified investments associated with the Executive Stock Unit Program (ESUP)	0.0	0.0
Level 3 | Liabilities associated with the ESUP
Liabilities:
Total liabilities	$ 0.0	$ 0.0