FINANCIAL INSTRUMENTS - Fair Value Level Disclosure (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets disclosed at fair value
Marketable securities	$ 265.1	$ 259.8
Total assets measured at fair value	16,524.1	19,562.2
Liabilities disclosed at fair value
Total liabilities measured at fair value	20,843.4	22,516.0
Level 2
Liabilities disclosed at fair value
Total liabilities measured at fair value	20,843.4	22,516.0
Level 3
Assets disclosed at fair value
Total assets measured at fair value	16,524.1	19,562.2
Recurring
Assets disclosed at fair value
Mutual funds	22.9	25.1
Corporate bonds	489.2	536.4
Marketable securities	265.1	259.8
Derivative instruments	1.1	0.2
Total assets measured at fair value	778.3	821.5
Liabilities disclosed at fair value
Derivative instruments	0.3	0.3
Total liabilities measured at fair value	0.3	0.3
Recurring | Level 1
Assets disclosed at fair value
Mutual funds	22.9	25.1
Marketable securities	34.2	26.2
Total assets measured at fair value	57.1	51.3
Recurring | Level 2
Assets disclosed at fair value
Corporate bonds	489.2	536.4
Marketable securities	230.9	233.6
Derivative instruments	1.1	0.2
Total assets measured at fair value	721.2	770.2
Liabilities disclosed at fair value
Derivative instruments	0.3	0.3
Total liabilities measured at fair value	$ 0.3	$ 0.3