LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES - LAE by Accident Year (Details) $ in Millions	Dec. 31, 2022 USD ($) claim	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Claims Development [Line Items]
Incurred Losses and ALAE—Net of Reinsurance	$ 1,285.7
IBNR	$ 70.0
Reported claims | claim	493,477
Cumulative Paid Losses and ALAE—Net of Reinsurance	$ 1,090.7
Loss and ALAE reserves—net of reinsurance	195.0
2017
Claims Development [Line Items]
Incurred Losses and ALAE—Net of Reinsurance	1.1	$ 1.1	$ 1.1	$ 1.1	$ 1.1	$ 1.2
IBNR	$ 0.0
Reported claims | claim	556
Cumulative Paid Losses and ALAE—Net of Reinsurance	$ 1.1	1.1	1.1	1.0	0.9	$ 0.6
2018
Claims Development [Line Items]
Incurred Losses and ALAE—Net of Reinsurance	48.3	48.7	49.6	48.3	42.3
IBNR	$ 0.2
Reported claims | claim	18,111
Cumulative Paid Losses and ALAE—Net of Reinsurance	$ 47.7	48.1	48.1	44.6	$ 20.6
2019
Claims Development [Line Items]
Incurred Losses and ALAE—Net of Reinsurance	306.0	304.7	306.3	287.3
IBNR	$ 1.5
Reported claims | claim	90,167
Cumulative Paid Losses and ALAE—Net of Reinsurance	$ 302.1	296.2	277.7	$ 177.0
2020
Claims Development [Line Items]
Incurred Losses and ALAE—Net of Reinsurance	286.2	287.7	295.9
IBNR	$ 3.9
Reported claims | claim	117,343
Cumulative Paid Losses and ALAE—Net of Reinsurance	$ 269.9	238.5	$ 182.0
2021
Claims Development [Line Items]
Incurred Losses and ALAE—Net of Reinsurance	348.1	341.6
IBNR	$ 14.3
Reported claims | claim	151,988
Cumulative Paid Losses and ALAE—Net of Reinsurance	$ 294.6	$ 179.4
2022
Claims Development [Line Items]
Incurred Losses and ALAE—Net of Reinsurance	296.0
IBNR	$ 50.1
Reported claims | claim	115,312
Cumulative Paid Losses and ALAE—Net of Reinsurance	$ 175.3