Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows provided by (used in) operating activities:
Net income (loss)	$ 25.6	$ (33.8)
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Amortization and depreciation	46.1	4.3
Share-based payments expense	0.0	1.5
Deferred income tax expense (benefit), net	2.6	(5.9)
Net investment and other (gains) losses	(6.2)	17.9
Undistributed earnings from alternative investment portfolio	(5.9)	0.2
Foreign currency exchange (gains) losses	(2.0)	2.7
Change in:
Accrued investment income	2.4	(0.3)
Receivables	47.1	613.8
Deferred acquisition costs	(25.0)	(6.5)
Ceded unearned premiums	2.3	(50.0)
Reserves for losses and loss adjustment expenses	0.6	(367.2)
Unearned premiums	(74.5)	(3.9)
Ceded reinsurance payable and funds held	28.0	(60.8)
Income taxes	(1.1)	(3.0)
Accrued underwriting expenses and other liabilities	(18.6)	(25.1)
Other, net	(35.1)	(44.8)
Cash (used in) provided by operating activities	(13.7)	39.1
Cash flows provided by (used in) investing activities:
Sales of fixed maturity investments	102.7	0.6
Maturities and mandatory calls of fixed maturity investments	63.7	32.5
Sales of equity securities	2.3	6.0
Sales of other investments	31.9	1.9
Purchases of fixed maturity investments	(1.0)	(1.7)
Purchases of equity securities	(0.1)	0.0
Purchases of other investments	(48.5)	(3.9)
Purchase of mortgage loans	(26.9)	0.0
Change in short-term investments	(637.8)	(215.0)
Settlements of foreign currency exchange forward contracts	0.8	5.1
Proceeds from business divestitures, net of cash transferred	0.0	54.3
Purchases of fixed assets, net	0.0	(1.4)
Cash used in investing activities	(512.9)	(121.6)
Cash flows provided by (used in) financing activities:
Additional debt borrowings	100.0	0.0
Issuance of common stock	100.0	0.0
Activity under stock incentive plans	0.0	0.5
Payment of cash dividends to preferred stockholders	(2.6)	(2.6)
Cash provided by (used in) financing activities	197.4	(2.1)
Net change in cash and restricted cash including balances classified as held-for-sale	(329.2)	(84.6)
Net change in cash balances classified as held-for-sale	0.0	70.8
Cash, restricted cash, and cash equivalents, beginning of period	791.6	50.2
Cash, restricted cash, and cash equivalents, end of period	$ 462.4	$ 36.4