Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net income (loss)	$ 761	$ 137	$ 419
Adjustments to reconcile net income to net cash flows provided by operating activities:
Non-cash interest and operating expenses	58	65	69
Net amortization of premium (discount) on investments	(37)	5	0
Provision (benefit) for deferred income taxes	(156)	(3)	(38)
Net realized investment losses (gains)	14	56	(15)
Equity in (earnings) losses of investees	(28)	39	(94)
Fair value gains (losses) on committed capital securities	35	(24)	28
Fair value losses (gains) on trading securities	(74)	34	0
Loss on extinguishment of debt	0	0	175
Gain on sale of asset management subsidiaries	(262)	0	0
Change in premiums receivable, net of premiums and commissions payable	(157)	74	0
Change in unearned premium reserve, net	26	(93)	(17)
Change in loss and loss adjustment expense reserve and salvage and subrogation recoverable, net	35	(1,207)	(99)
Change in current income taxes	72	(106)	64
Change in credit derivative assets and liabilities, net	(112)	8	54
Other	(90)	(37)	(8)
Cash flows from consolidated investment vehicles:
Purchases of securities	(340)	(3,201)	(4,957)
Sales of securities	675	1,513	2,161
Maturities and paydowns of securities	60	156	430
Proceeds from (purchases of) money market funds	66	6	(6)
Purchases to cover securities sold short	0	(223)	(621)
Proceeds from securities sold short	0	188	618
Other changes in consolidated investment vehicles	(85)	134	(100)
Net cash flows provided by (used in) operating activities	461	(2,479)	(1,937)
Fixed-maturity securities, available for sale:
Purchases	(540)	(371)	(1,236)
Sales	862	717	428
Maturities and paydowns	746	682	1,148
Short-term investments with original maturities of over three months:
Purchases	(16)	(63)	0
Sales	4	0	0
Maturities and paydowns	36	36	36
Net sales (purchases) of short-term investments with original maturities of less than three months	(872)	439	(410)
Fixed-maturity securities, trading:
Sales	0	121	0
Maturities and paydowns	63	87	0
Purchases of other invested assets	(198)	(25)	(79)
Sales and return of capital of other invested assets	29	36	80
Paydowns on financial guaranty variable interest entities’ assets	175	84	62
Other	(3)	(3)	(6)
Net cash flows provided by (used in) investing activities	286	1,740	23
Cash flows from financing activities:
Dividends paid	(67)	(64)	(66)
Repurchases of common shares	(199)	(500)	(496)
Net paydowns of financial guaranty variable interest entities’ liabilities	(149)	(99)	(53)
Net proceeds from issuance of debt	345	0	889
Redemptions and purchases of debt, including make-whole payment	(330)	(2)	(620)
Other	(19)	(6)	26
Cash flows from consolidated investment vehicles:
Proceeds from issuance of collateralized loan obligations	0	1,372	3,276
Repayment of collateralized loan obligations	(1)	(373)	(824)
Proceeds from issuance of warehouse financing debt	0	991	1,338
Repayment of warehouse financing debt	(166)	(796)	(1,537)
Contributions from noncontrolling interests to consolidated investment vehicles	0	74	39
Distributions to noncontrolling interests from consolidated investment vehicles	(80)	(26)	(12)
Proceeds from (Repayments of) Lines of Credit	(4)	41	0
Net cash flows provided by (used in) financing activities	(670)	612	1,960
Effect of foreign exchange rate changes	2	(8)	(2)
Increase (decrease) in cash and cash equivalents and restricted cash	79	(135)	44
Cash and cash equivalents and restricted cash at beginning of period	207	342	298
Cash and cash equivalents and restricted cash at end of period	286	207	342
Supplemental cash flow information
Income taxes paid (received)	4	105	24
Interest paid on long-term debt	77	77	80
Supplemental disclosure of non-cash activities:
Fixed-maturity securities, available-for-sale, received as salvage	1	986	0
Fixed-maturity securities, available-for-sale, ceded to a reinsurer	0	27	0
Fixed-maturity securities, trading, received as salvage	0	549	0
Fixed-maturity securities, trading, ceded to a reinsurer	0	6	0
Debt securities of financial guaranty variable interest entities received as salvage	0	234	0
Contributions from noncontrolling interests	20	36	1
Distributions to noncontrolling interests	27	56	1
Assets acquired	437	0	0
Assets transferred	240	0	0
Liabilities transferred	66	0	0
Reconciliation of cash and cash equivalents and restricted cash to the consolidated balance sheets:
Cash	97	107	120
Restricted cash (included in other assets)	0	1	2
Cash of financial guaranty variable interest entities	154	2	0
Cash and cash equivalents of consolidated vehicles	35	97	220
Cash and cash equivalents and restricted cash at the end of period	$ 286	$ 207	$ 342