Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Cash flows from operating activities:
Net income attributable to common shareholders	$ (33)	$ 2
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(1)	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	(33)	2
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	0	0
Amortization of bond premium and discount	(3)	(3)
Share-based compensation	3	5
Unearned premiums, net	6	(11)
Losses and loss expenses, net	143	(6)
Ceded premiums payable	(1)	7
Premium receivables	(3)	6
Accrued interest payable	(37)	24
Amortization of Intangible Assets	7	14
Net investment gains (losses), including impairments	4	(10)
Variable interest entity activities	1	(22)
Derivative assets and liabilities	14	(46)
Other, net	(25)	48
Net Cash Provided by (Used in) Operating Activities, Total	77	9
Proceeds from Sale of Debt Securities, Available-for-Sale	63	141
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from matured bonds	6	20
Purchases of bonds	(104)	(33)
Proceeds from sales of other invested assets	41	45
Purchases of other invested assets	(14)	(25)
Change in short-term investments	146	(114)
Change in cash collateral	(16)	54
Proceeds from paydowns of consolidated VIE assets	57	47
Other, net	8	0
Net cash provided by investing activities	441	136
Net Cash Provided by (Used in) Financing Activities [Abstract]
Tax payments related to shares withheld for share-based compensation plans	(5)	(3)
Proceeds from (Payments to) Noncontrolling Interests	0	0
Payments of consolidated VIE liabilities	(174)	(49)
Net cash used in financing activities	(276)	(52)
Effect of foreign exchange on cash, cash equivalents and restricted cash	0	0
Net cash flow	243	93
Cash, cash equivalents, and restricted cash at beginning of period	61	23
Cash, cash equivalents, and restricted cash at end of period	304	116
Change in cash collateral	(16)	54
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	254	0
Change in cash collateral	$ 254	$ 0