LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES - Schedule of Reserve Balance (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross loss and LAE reserves, January 1	$ 413.2	$ 284.2
Reinsurance recoverable on unpaid losses	(48.0)	(43.8)
Net loss and LAE reserves, January 1	377.4	275.5	$ 365.2	$ 240.4
Net incurred loss and LAE related to:
Current year	218.7	169.4
Prior years	(13.1)	(3.0)
Net losses and LAE incurred	205.6	166.4
Net paid loss and LAE related to:
Current year	69.6	52.1
Prior years	123.8	79.2
Total paid	193.4	131.3
Net loss and LAE reserves, March 31	377.4	275.5
Plus reinsurance recoverable on unpaid losses	41.1	46.5
Gross loss and LAE reserves, March 31	$ 418.5	$ 322.0