Fair Value (Table of reconciliation for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,844	$ 1,614	$ 1,676	$ 1,578
Reported in Net investment gains (losses)	$ (1)	$ 0	$ (1)	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net investment losses	Net investment losses	Net investment losses	Net investment losses
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Other comprehensive income (loss)	Other comprehensive income (loss)	Other comprehensive income (loss)	Other comprehensive income (loss)
Reported in Other comprehensive income (loss)	$ (23)	$ (139)	$ 9	$ (247)
Total realized and unrealized investment gains (losses)	(20)	(135)	11	(238)
Purchases	155	143	291	362
Sales	(2)	(5)	(2)	(10)
Settlements	(22)	(51)	(34)	(90)
Transfers into Level 3	11	14	34	29
Transfers out of Level 3	(43)	0	(53)	(51)
Balance, Ending, Assets	1,923	1,580	1,923	1,580
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(1)	(3)	(7)	(1)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(23)	(138)	8	(246)
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	912	915	810	937
Reported in Net investment gains (losses)	0	(1)	0	(2)
Reported in Other comprehensive income (loss)	(15)	(82)	9	(153)
Total realized and unrealized investment gains (losses)	(15)	(83)	9	(155)
Purchases	68	51	149	118
Sales	0	0	0	(5)
Settlements	(5)	(37)	(8)	(59)
Transfers into Level 3	11	0	11	10
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	971	846	971	846
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	0	0	0
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(15)	(81)	9	(153)
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	44	51	43	56
Reported in Net investment gains (losses)	0	0	0	0
Reported in Other comprehensive income (loss)	(1)	(5)	0	(10)
Total realized and unrealized investment gains (losses)	(1)	(5)	0	(10)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	43	46	43	46
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	0	0	0
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(1)	(5)	0	(10)
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	859	604	788	556
Reported in Net investment gains (losses)	(1)	3	(1)	5
Reported in Other comprehensive income (loss)	(7)	(52)	0	(84)
Total realized and unrealized investment gains (losses)	(3)	(44)	9	(73)
Purchases	87	92	142	232
Sales	0	(2)	0	(2)
Settlements	(17)	(23)	(26)	(40)
Transfers into Level 3	0	14	23	19
Transfers out of Level 3	(43)	0	(53)	(51)
Balance, Ending, Assets	883	641	883	641
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	0	0	0
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(7)	(52)	(1)	(83)
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	29	44	35	29
Reported in Net investment gains (losses)	0	(2)	0	(3)
Reported in Other comprehensive income (loss)	0	0	0	0
Total realized and unrealized investment gains (losses)	(1)	(3)	(7)	0
Purchases	0	0	0	12
Sales	(2)	(3)	(2)	(3)
Settlements	0	9	0	9
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	26	47	26	47
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(1)	(3)	(7)	(1)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	0	0	0	0
Reported in Net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment income	4	4	3	9
Reported in Net investment income | Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment income	0	0	0	0
Reported in Net investment income | States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment income	0	0	0	0
Reported in Net investment income | Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment income	5	5	10	6
Reported in Net investment income | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment income	$ (1)	$ (1)	$ (7)	$ 3