LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross loss and LAE reserves, January 1			$ 140.7	$ 33.3
Reinsurance recoverable on unpaid losses			(18.9)	(11.4)
Net loss and LAE reserves, January 1			121.8	21.9
Net incurred loss and LAE related to:
Current year			282.0	204.4
Prior years			21.3	6.1
Total incurred	$ 76.1	$ 100.9	303.3	210.5
Net paid loss and LAE related to:
Current year			165.8	125.2
Prior years			100.4	23.3
Total paid			266.2	148.5
Net loss and LAE reserves, September 30	158.9	83.9	158.9	83.9
Plus reinsurance recoverable on unpaid losses	66.4	26.5	66.4	26.5
Gross loss and LAE reserves, September 30	$ 225.3	$ 110.4	$ 225.3	$ 110.4