Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net income (loss)	$ 419	$ 368	$ 401
Adjustments to reconcile net income to net cash flows provided by operating activities:
Non-cash interest and operating expenses	69	54	34
Net amortization of premium (discount) on investments	0	(9)	(35)
Provision (benefit) for deferred income taxes	(38)	58	65
Net realized investment losses (gains)	(15)	(18)	(22)
Equity in earnings of investees	(94)	(27)	(4)
Loss on extinguishment of debt	175	0	0
Change in premiums receivable, net of premiums and commissions payable	0	(102)	(388)
Change in unearned premium reserve, net	(17)	19	244
Change in loss and loss adjustment expense reserve, net	(99)	(174)	(528)
Change in current income taxes	64	9	1
Change in credit derivative assets and liabilities, net	54	(85)	(22)
Other	20	8	(3)
Cash flows from consolidated investment vehicles:
Purchases of securities	(4,957)	(2,053)	(267)
Sales of securities	2,161	1,156	13
Maturities and paydowns of securities	430	71	5
Proceeds from (purchases of) money market funds	(6)	(108)	0
Purchases to cover securities sold short	(621)	(460)	0
Proceeds from securities sold short	618	509	0
Other changes in consolidated investment vehicles	(100)	(69)	(3)
Net cash flows provided by (used in) operating activities	(1,937)	(853)	(509)
Fixed-maturity securities:
Purchases	(1,236)	(1,380)	(873)
Sales	428	779	1,805
Maturities and paydowns	1,148	878	781
Short-term investments with original maturities of over three months:
Purchases	0	(85)	(229)
Sales	0	5	2
Maturities and paydowns	36	73	316
Net sales (purchases) of short-term investments with original maturities of less than three months	(410)	430	(623)
Acquisitions, net of cash acquired (see Note 2)	0	0	(145)
Sales and return of capital of other invested assets	80	23	36
Purchases of other invested assets	(79)	(19)	(88)
Paydowns on financial guaranty variable interest entities’ assets	62	83	139
Sales of financial guaranty variable interest entities’ assets	0	0	51
Other	(6)	1	(3)
Net cash flows provided by (used in) investing activities	23	788	1,169
Cash flows from financing activities:
Dividends paid	(66)	(69)	(74)
Repurchases of common shares	(496)	(446)	(500)
Net paydowns of financial guaranty variable interest entities’ liabilities	(53)	(77)	(181)
Issuance of long-term debt, net of issuance costs	889	0	0
Redemptions and purchases of debt, including make-whole payment	(620)	(22)	(4)
Other	26	(10)	(15)
Cash flows from consolidated investment vehicles:
Proceeds from issuance of collateralized loan obligations	3,276	738	482
Repayment of collateralized loan obligations	(824)	0	0
Proceeds from issuance of warehouse financing debt	1,338	234	0
Repayment of warehouse financing debt	(1,537)	(210)	(306)
Contributions from noncontrolling interests to consolidated investment vehicles	39	88	18
Distributions to noncontrolling interests from consolidated investment vehicles	(12)	(43)	(4)
Net cash flows provided by (used in) financing activities	1,960	183	(584)
Effect of foreign exchange rate changes	(2)	(3)	3
Increase (decrease) in cash and cash equivalents and restricted cash	44	115	79
Cash and cash equivalents and restricted cash at beginning of period	298	183	104
Cash and cash equivalents and restricted cash at end of period	342	298	183
Supplemental cash flow information
Income taxes paid (received)	24	(25)	4
Interest paid on long-term debt	80	81	84
Supplemental disclosure of non-cash investing activities:
Purchases of fixed-maturity securities	0	(1)	(188)
Sales of fixed-maturity securities	0	1	44
Sales and return of capital of other invested assets	6	1	0
Purchases of other invested assets	(6)	0	0
Reconciliation of cash and cash equivalents and restricted cash to the consolidated balance sheets:
Cash	120	162	169
Restricted cash (included in other assets)	2	2	0
Cash and cash equivalents of consolidated investment vehicles (see Note 9)	220	134	14
Cash and cash equivalents and restricted cash at the end of period	$ 342	$ 298	$ 183