INVESTMENTS - SCHEDULE OF REALIZED GAIN (LOSS) ON INVESTMENTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Realized investment gains (losses):
Total investment gains (losses)	$ (17.9)	$ 21.3	$ (18.4)
Change in allowance for credit losses and impairments of other investments	(52.6)	12.2	(18.5)
Change in fair value of equity securities	(2.9)	(7.3)	(1.8)
Other changes in fair value	(62.0)	(7.1)	2.5
Other investment gains (losses)	(117.5)	(2.2)	(17.8)
Total investment gains (losses)	(135.4)	19.1	(36.2)
Variable interest entities change in allowance for current expected credit losses	(1.8)	11.4	(5.2)
Increase (decrease) in equity securities, FV-NI, held at end of period	(7.3)	(7.8)	(1.7)
Change in estimated fair value of trading securities	(43.3)	(3.1)	0.4
Total fixed maturities, available for sale
Realized investment gains (losses):
Gross realized gains on sales of fixed maturities, available for sale	99.8	51.6	48.6
Gross realized losses on sales of fixed maturities, available for sale	(104.0)	(20.4)	(53.7)
Equity securities, net	(8.3)	(2.9)	(3.3)
Other, net	$ (5.4)	$ (7.0)	$ (10.0)