Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net income attributable to common shareholders	$ (8,000)	$ 19,000
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	1,000	(1,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	(9,000)	21,000
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	2,000	1,000
Amortization of bond premium and discount	(13,000)	(10,000)
Share-based compensation	6,000	12,000
Unearned premiums, net	(2,000)	(46,000)
Losses and loss expenses, net	3,000	66,000
Ceded premiums payable	75,000	56,000
Premium receivables	(52,000)	(8,000)
Accrued interest payable	40,000	(13,000)
Amortization of Intangible Assets	33,000	21,000
Net investment gains (losses), including impairments	(3,000)	7,000
Variable interest entity activities	(5,000)	0
Other, net	(46,000)	7,000
Net Cash Provided by (Used in) Operating Activities, Total	28,000	112,000
Proceeds from Sale of Debt Securities, Available-for-Sale	193,000	113,000
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from matured bonds	126,000	58,000
Purchases of bonds	(358,000)	(291,000)
Proceeds from sales of other invested assets	101,000	189,000
Purchases of other invested assets	(132,000)	(62,000)
Change in short-term investments	147,000	125,000
Change in cash collateral	(2,000)	(29,000)
Proceeds from paydowns of consolidated VIE assets	127,000	161,000
Other, net	(8,000)	8,000
Net cash provided by (used in) investing activities	(200,000)	521,000
Net Cash Provided by (Used in) Financing Activities [Abstract]
Tax payments related to shares withheld for share-based compensation plans	(1,000)	(5,000)
Proceeds from (Payments to) Noncontrolling Interests	(2,000)	(1,000)
Payments of consolidated VIE liabilities, net	(131,000)	(285,000)
Net cash provided by (used in) financing activities	14,000	(392,000)
Effect of foreign exchange on cash, cash equivalents and restricted cash	0	0
Net cash flow	(158,000)	241,000
Cash, cash equivalents, and restricted cash at beginning of period	274,000	61,000
Cash, cash equivalents, and restricted cash at end of period	117,000	302,000
Change in cash collateral	(2,000)	(29,000)
Treasury Stock, Value, Acquired, Cost Method	0	(5,000)
Payments to Acquire Businesses, Net of Cash Acquired	(215,000)	(7,000)
Proceeds from Divestiture of Businesses, Net of Cash Divested	14,000
Proceeds from Short-Term Debt	147,000
Net Cash Provided by (Used in) Financing Activities	14,000	(392,000)
Net Cash Provided by (Used in) Investing Activities	(200,000)	521,000
Net Cash Provided by (Used in) Operating Activities	28,000	112,000
Tier 2 Notes
Net Cash Provided by (Used in) Financing Activities [Abstract]
Repayments of Secured Debt	0	(97,000)
Repayments of Secured Debt	0	97,000
Variable Interest Entity, Primary Beneficiary [Member]
Net Cash Provided by (Used in) Investing Activities [Abstract]
Change in cash collateral	(195,000)	254,000
Change in cash collateral	$ (195,000)	$ 254,000