INVESTMENTS IN VARIABLE INTEREST ENTITIES - SCHEDULE OF IMPACT ON BALANCE SHEET OF CONSOLIDATING VARIABLE INTEREST ENTITIES (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2020
Assets:
Investments held by variable interest entities	$ 1,077.6	$ 1,199.6	$ 1,178.7
Cash and cash equivalents held by variable interest entities	69.2	99.6
Accrued investment income	235.6	216.4
Income tax assets, net	1,165.5	118.3	437.5
Other assets	580.8	519.1
Total assets	33,339.2	36,204.4	$ 33,613.1
Liabilities:
Other liabilities	693.9	830.9
Borrowings related to variable interest entities	1,104.6	1,147.9
Total liabilities	31,938.4	30,944.7
Investments held by variable interest entities - corporate securities
Assets:
Investments held by variable interest entities	1,077.6	1,199.6
Notes receivable of VIEs held by subsidiaries	(113.8)	(113.8)
Cash and cash equivalents held by variable interest entities	69.2	99.6
Accrued investment income	3.5	1.6
Income tax assets, net	19.6	8.4
Other assets	1.7	6.2
Total assets	1,057.8	1,201.6
Liabilities:
Other liabilities	26.9	85.2
Borrowings related to variable interest entities	1,104.6	1,147.9
Notes payable of VIEs held by subsidiaries	0.0	0.0
Total liabilities	1,131.5	1,233.1
Investments held by variable interest entities - corporate securities | VIEs
Assets:
Investments held by variable interest entities	1,077.6	1,199.6
Notes receivable of VIEs held by subsidiaries	0.0	0.0
Cash and cash equivalents held by variable interest entities	69.2	99.6
Accrued investment income	3.5	1.6
Income tax assets, net	19.6	8.4
Other assets	2.5	7.1
Total assets	1,172.4	1,316.3
Liabilities:
Other liabilities	29.3	89.5
Borrowings related to variable interest entities	1,104.6	1,147.9
Notes payable of VIEs held by subsidiaries	126.1	126.1
Total liabilities	1,260.0	1,363.5
Investments held by variable interest entities - corporate securities | Eliminations
Assets:
Investments held by variable interest entities	0.0	0.0
Notes receivable of VIEs held by subsidiaries	(113.8)	(113.8)
Cash and cash equivalents held by variable interest entities	0.0	0.0
Accrued investment income	0.0	0.0
Income tax assets, net	0.0	0.0
Other assets	(0.8)	(0.9)
Total assets	(114.6)	(114.7)
Liabilities:
Other liabilities	(2.4)	(4.3)
Borrowings related to variable interest entities	0.0	0.0
Notes payable of VIEs held by subsidiaries	(126.1)	(126.1)
Total liabilities	$ (128.5)	$ (130.4)