SCHEDULE IV - REINSURANCE (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Premiums earned
Net earned premiums	$ 1,440.9	$ 1,076.7	$ 664.2
HG Global/BAM
Premiums earned
Gross Amount	28.7	28.6	23.2
Ceded	0.0	0.0	0.0
Assumed	2.5	4.7	3.7
Net earned premiums	$ 31.2	$ 33.3	$ 26.9
Percentage of Amount Assumed to Net	8.00%	14.10%	13.80%
Ark/WM Outrigger
Premiums earned
Gross Amount	$ 848.1	$ 655.5	$ 556.0
Ceded	(364.0)	(280.8)	(249.1)
Assumed	925.6	668.7	330.4
Net earned premiums	$ 1,409.7	$ 1,043.4	$ 637.3
Percentage of Amount Assumed to Net	65.70%	64.10%	51.80%