INVESTMENTS - SUMMARY OF CHANGES IN THE ALLOWANCE FOR CURRENT EXPECTED CREDIT LOSSES RELATED TO MORTGAGE LOANS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Mortgage loans
Allowance for credit losses at beginning of period	$ 5.6	$ 11.8	$ 6.7
Current period provision for expected credit losses	2.4	(6.2)	5.1
Initial allowance recognized for purchased financial assets with credit deterioration	0.0	0.0	0.0
Write-offs charged against the allowance	0.0	0.0	0.0
Recoveries of amounts previously written off	0.0	0.0	0.0
Allowance for credit losses at end of period	$ 8.0	$ 5.6	$ 11.8