INVESTMENTS - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Investment Income [Line Items]
Total	$ 7.3	$ 5.9	$ 5.6
Investment expense	(2.3)	(0.5)	(0.4)
Net investment income	5.0	5.4	5.2
Interest on bonds
Net Investment Income [Line Items]
Total	2.4	4.2	1.8
Interest on deposits and cash equivalents
Net Investment Income [Line Items]
Total	1.1	1.7	3.8
Other investments
Net Investment Income [Line Items]
Total	$ 3.8	$ 0.0	$ 0.0