Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Statement of Cash Flows [Abstract]
Net cash flows provided by (used in) operating activities				$ (664)	$ (365)
Fixed-maturity securities:
Purchases				(856)	(688)
Sales	$ 137		$ 405	627	1,306
Maturities and paydowns				642	664
Short-term investments with maturities of over three months:
Purchases				(238)	(216)
Sales				41	2
Maturities and paydowns				198	206
Net sales (purchases) of short-term investments with original maturities of less than three months				415	(404)
Paydowns on financial guaranty variable interest entities’ assets				67	119
Sales of financial guaranty variable interest entities' assets				0	51
Sales and return of capital of other invested assets				21	35
Other				(11)	(5)
Net cash flows provided by (used in) investing activities				906	1,070
Financing activities
Dividends paid				(53)	(56)
Repurchases of common stock				(320)	(340)
Net paydowns of financial guaranty variable interest entities’ liabilities				(63)	(162)
Paydown of long-term debt				(22)	(4)
Other				(12)	(16)
Proceeds from issuance of collateralized loan obligations				361	0
Proceeds from issuance of warehouse financing debt				47	0
Contributions from noncontrolling interests to investment vehicles				69	0
Distributions to noncontrolling interests from investment vehicles				(19)	0
Net cash flows provided by (used in) financing activities				(12)	(578)
Effect of foreign exchange rate changes				(7)	(2)
Increase (decrease) in cash and restricted cash				223	125
Cash and restricted cash at beginning of period		$ 229		183	104	$ 104
Supplemental cash flow information
Income taxes				1
Income taxes					(2)
Interest on long-term debt				49	51
Purchases of fixed-maturity investments				(1)	(188)
Sales of fixed-maturity investments				1	44
Cash	223	169	229	223	229	169
Restricted cash (included in other assets)	1		0	1	0
Cash of consolidated investment vehicles (see Note 11)	182		0	182	0
Cash and restricted cash at end of period	$ 406	$ 183	$ 229	$ 406	$ 229	$ 183