Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities:
Net income attributable to common shareholders	$ (47)	$ 7
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(1)	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	(46)	8
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	1	1
Amortization of bond premium and discount	(6)	(6)
Share-based compensation	8	10
Unearned premiums, net	(51)	(25)
Losses and loss expenses, net	144	(13)
Ceded premiums payable	57	11
Premium receivables	(7)	12
Accrued interest payable	(26)	48
Amortization of Intangible Assets	13	28
Net investment gains (losses), including impairments	8	(17)
Variable interest entity activities	1	(15)
Derivative assets and liabilities	25	(54)
Other, net	(21)	81
Net Cash Provided by (Used in) Operating Activities, Total	101	11
Proceeds from Sale of Debt Securities, Available-for-Sale	107	387
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from matured bonds	31	69
Purchases of bonds	(226)	(189)
Proceeds from sales of other invested assets	108	108
Purchases of other invested assets	(42)	(74)
Change in short-term investments	170	(2)
Change in cash collateral	(37)	56
Proceeds from paydowns of consolidated VIE assets	113	83
Other, net	10	2
Net cash provided by investing activities	489	440
Net Cash Provided by (Used in) Financing Activities [Abstract]
Tax payments related to shares withheld for share-based compensation plans	(8)	(3)
Proceeds from (Payments to) Noncontrolling Interests	(1)	1
Payments of consolidated VIE liabilities	(235)	(359)
Net cash used in financing activities	(343)	(434)
Effect of foreign exchange on cash, cash equivalents and restricted cash	1	(1)
Net cash flow	248	16
Cash, cash equivalents, and restricted cash at beginning of period	61	23
Cash, cash equivalents, and restricted cash at end of period	309	39
Change in cash collateral	(37)	56
Net realized gains on extinguishment of debt	0	(57)
Payment for Debt Extinguishment or Debt Prepayment Cost	0	(58)
Treasury Stock, Value, Acquired, Cost Method	(3)	(14)
Tier 2 Notes
Net Cash Provided by (Used in) Financing Activities [Abstract]
Repayments of Secured Debt	(97)	0
Repayments of Secured Debt	97	0
Variable Interest Entity, Primary Beneficiary [Member]
Net Cash Provided by (Used in) Investing Activities [Abstract]
Change in cash collateral	256	0
Change in cash collateral	$ 256	$ 0