FAIR VALUE OF ASSETS AND LIABILITIES - Fair Value of Financial Instruments Held by Consolidated Investments (Details) - USD ($) $ in Millions		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		$ 1,896.4	$ 1,408.4	$ 1,049.0
Restricted cash	[1]	0.0	129.2	$ 0.0
Foreign time deposits		30.4	29.9
Assets held for policyholders		1,893.6	7,582.1
Policyholder payables		(1,893.6)	(7,582.1)
Derivative asset		1.6	5.1
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents		1,896.4	1,408.4
Restricted cash		0.0	129.2
Equity investments		337.9	360.3
Foreign time deposits		30.4	29.9
Assets held for policyholders		1,893.6	7,582.1
Policyholder payables		(1,893.6)	(7,582.1)
Contingent consideration liability		(1.3)	(18.6)
Fair Value | Total Return Swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative asset		$ 1.6	$ 5.1

[1] Restricted cash of $129.2 million as of December 31, 2020 is recorded in Other assets on the Consolidated Balance Sheets.