FINANCIAL INSTRUMENTS - Fair Value Level Disclosure (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Assets disclosed at fair value
Marketable securities	$ 259.8	$ 266.4
U.S. Treasury bonds		24.9
Total assets measured at fair value	19,562.2	19,468.2
Liabilities disclosed at fair value
Total liabilities measured at fair value	22,516.0	25,150.9
Level 2
Liabilities disclosed at fair value
Total liabilities measured at fair value	22,516.0	25,150.9
Level 3
Assets disclosed at fair value
Total assets measured at fair value	19,562.2	19,468.2
Recurring
Assets disclosed at fair value
Mutual funds	25.1	23.2
Corporate bonds	536.4	491.5
Marketable securities	259.8	266.4
U.S. Treasury bonds		24.9
Derivative instruments	0.2	3.8
Total assets measured at fair value	821.5	809.8
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	25.1	23.2
Marketable securities	26.2	25.0
U.S. Treasury bonds		24.9
Total assets measured at fair value	51.3	73.1
Recurring | Level 2
Assets disclosed at fair value
Corporate bonds	536.4	491.5
Marketable securities	233.6	241.4
Derivative instruments	0.2	3.8
Total assets measured at fair value	770.2	736.7
Liabilities disclosed at fair value
Derivative instruments	0.3	0.3
Total liabilities measured at fair value	$ 0.3	$ 0.3