Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities:
Net income attributable to common shareholders	$ 19,000	$ (47,000)
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(1,000)	(1,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	20,000	(46,000)
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	1,000	1,000
Amortization of bond premium and discount	(8,000)	(6,000)
Share-based compensation	2,000	8,000
Unearned premiums, net	(5,000)	(51,000)
Losses and loss expenses, net	(15,000)	144,000
Ceded premiums payable	50,000	57,000
Premium receivables	(27,000)	(7,000)
Accrued interest payable	25,000	(26,000)
Amortization of Intangible Assets	21,000	13,000
Net investment gains (losses), including impairments	(4,000)	8,000
Variable interest entity activities	(2,000)	1,000
Other, net	(24,000)	4,000
Net Cash Provided by (Used in) Operating Activities, Total	32,000	101,000
Proceeds from Sale of Debt Securities, Available-for-Sale	26,000	107,000
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from matured bonds	76,000	31,000
Purchases of bonds	(215,000)	(226,000)
Proceeds from sales of other invested assets	41,000	108,000
Purchases of other invested assets	(94,000)	(42,000)
Change in short-term investments	139,000	170,000
Change in cash collateral	5,000	(37,000)
Proceeds from paydowns of consolidated VIE assets	84,000	113,000
Other, net	(1,000)	10,000
Net cash provided by (used in) investing activities	(120,000)	489,000
Net Cash Provided by (Used in) Financing Activities [Abstract]
Tax payments related to shares withheld for share-based compensation plans	(1,000)	(8,000)
Proceeds from (Payments to) Noncontrolling Interests	(1,000)	(1,000)
Payments of consolidated VIE liabilities, net	(87,000)	(235,000)
Net cash used in financing activities	(89,000)	(343,000)
Effect of foreign exchange on cash, cash equivalents and restricted cash	0	1,000
Net cash flow	(178,000)	248,000
Cash, cash equivalents, and restricted cash at beginning of period	274,000	61,000
Cash, cash equivalents, and restricted cash at end of period	97,000	309,000
Change in cash collateral	5,000	(37,000)
Treasury Stock, Value, Acquired, Cost Method		(3,000)
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	(180,000)	256,000
Change in cash collateral	$ (180,000)	$ 256,000