FAIR VALUE MEASUREMENTS - Schedule of fair value hierarchy of financial instruments held (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Assets:
Cash and cash equivalents	$ 140.0	$ 143.5
Financial investments	131.8	47.3
Accounts receivable	252.2	217.3
Income tax receivable		17.2
Total assets	524.0	425.3
Liabilities:
Accounts payable	11.1	43.2
Section 31 fees payable	189.9	105.6
Contingent consideration liabilities	2.2	56.6
Debt	1,214.1	1,237.9
Total liabilities	1,417.3	1,443.3
Level 1
Assets:
Cash and cash equivalents	140.0	143.5
Financial investments	131.8	47.3
Accounts receivable	252.2	217.3
Income tax receivable		17.2
Total assets	524.0	425.3
Level 2
Liabilities:
Accounts payable	11.1	43.2
Section 31 fees payable	189.9	105.6
Debt	1,214.1	1,237.9
Total liabilities	1,415.1	1,386.7
Level 3
Liabilities:
Contingent consideration liabilities	2.2	56.6
Total liabilities	$ 2.2	$ 56.6