LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross loss and LAE reserves, January 1	$ 320.2	$ 237.2
Reinsurance recoverable on unpaid losses	(79.5)	(79.6)
Net loss and LAE reserves, January 1	240.7	157.6
Net incurred loss and LAE related to:
Current year	96.8	69.8
Prior years	(0.1)	(9.9)
Total incurred	96.7	59.9
Net paid loss and LAE related to:
Current year	36.4	25.3
Prior years	57.7	35.3
Total paid	94.1	60.6
Net loss and LAE reserves, March 31	243.3	156.9
Plus reinsurance recoverable on unpaid losses	65.1	83.8
Gross loss and LAE reserves, March 31	$ 308.4	$ 240.7