INVESTMENTS - TOTAL INVESTMENT GAINS (LOSSES) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Gain (Loss) on Securities [Line Items]
Total realized investment gains (losses)	$ 18.8	$ (6.0)
Change in allowance for credit losses	(30.7)	9.6
Change in fair value of equity securities	(1.2)	(1.8)
Other changes in fair value	(19.6)	(4.6)
Other investment gains (losses)	(51.5)	3.2
Net realized investment gains (losses)	(32.7)	(2.8)
Variable interest entities, change in allowance for current expected credit losses	(2.2)	9.7
Increase (Decrease) in Equity Securities, FV-NI, Held at End of Period	(5.2)	(1.3)
Change in estimated fair value of trading securities	(12.8)	(1.6)
Total fixed maturities, available for sale
Gain (Loss) on Securities [Line Items]
Gross realized gains on sale	54.8	13.2
Gross realized losses on sale	(30.6)	(13.8)
Equity securities, net	(4.7)	0.0
Other, net	$ (0.7)	$ (5.4)