CONSOLIDATED STATEMENTS OF INCOME (LOSS) - USD ($) $ in Millions	2 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2023	Nov. 15, 2023	Dec. 31, 2024	Dec. 31, 2022
Premiums and other revenue:
Net earned premiums	$ 162.3	$ 1,225.9	$ 1,089.8	$ 1,740.4
Net investment income	28.6	121.3	249.8	129.8
Net investment and other gains (losses):
Net realized investment and other gains (losses)	0.1	(20.4)	11.6	(115.9)
Change in fair value recognized	(0.2)	(0.2)	14.2	3.1
Change in allowance for credit losses	(0.2)	(2.1)	(5.8)	(2.5)
Total net investment and other gains (losses)	(0.3)	(22.7)	20.0	(115.3)
Total revenue	190.6	1,324.5	1,359.6	1,754.9
Expenses:
Losses and loss adjustment expenses	94.2	1,043.2	1,018.3	1,166.9
Underwriting, acquisition and general expenses	77.2	419.0	477.0	670.7
Non-operating expenses	13.1	41.1	17.6	51.5
Interest expense	3.5	29.8	38.1	26.8
Fee and other (income) expense, net	(0.2)	(0.3)	(0.1)	(1.3)
Foreign currency exchange (gains) losses	0.6	1.8	(1.0)	(5.0)
Impairment of goodwill and intangibles	0.0	0.0	0.0	28.5
Total expenses	188.4	1,534.6	1,549.9	1,938.1
Income (loss) before income taxes	2.2	(210.1)	(190.3)	(183.2)
Income tax provision (benefit)	1.3	0.3	(42.2)	(8.0)
Net income (loss)	0.9	(210.4)	(148.1)	(175.2)
Dividends on Series A Preferred stock	0.0	10.5	10.5	10.5
Net income (loss) attributable to common shareholders, diluted	0.9	(220.9)	(158.6)	(185.7)
Net income (loss) attributable to common shareholders, basic	0.9	$ (220.9)	(158.6)	$ (185.7)
Net income (loss) attributable to common stockholders per share of common stock:
Basic (in dollars per share)		$ (6.28)		$ (5.31)
Diluted (in dollars per share)		(6.28)		(5.31)
Dividend declared per common share (in dollars per share)		$ 0		$ 1.24
Weighted average common stock:
Basic (in shares)		35,166,679		34,980,608
Diluted (in shares)		35,166,679		34,980,608
Net realized investment gains (losses) before other-than-temporary impairment losses	(0.3)	$ (19.8)	20.0	$ (79.2)
Other-than-temporary impairment losses recognized in earnings:
Other-than-temporary impairment losses on fixed maturities, recognized in earnings	$ 0.0	$ (2.9)	$ 0.0	$ (36.1)