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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 2,007	$ 1,844	$ 2,014	$ 1,676
Reported in Net investment gains (losses)	(3)	(1)	$ (7)	$ (1)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			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)
Reported in Other comprehensive income (loss)	(19)	(23)	$ (37)	$ 9
Total realized and unrealized investment gains (losses)	(17)	(20)	(27)	11
Purchases	130	155	222	291
Sales	(5)	(2)	(33)	(2)
Settlements	(42)	(22)	(95)	(34)
Transfers into Level 3	0	11	11	34
Transfers out of Level 3	0	(43)	(19)	(53)
Balance, Ending, Assets	2,073	1,923	2,073	1,923
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	(1)	2	(7)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(19)	(23)	(39)	8
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,082	912	1,045	810
Reported in Net investment gains (losses)	0	0	0	0
Reported in Other comprehensive income (loss)	(8)	(15)	(20)	9
Total realized and unrealized investment gains (losses)	(8)	(15)	(20)	9
Purchases	72	68	146	149
Sales	0	0	0	0
Settlements	(17)	(5)	(53)	(8)
Transfers into Level 3	0	11	11	11
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	1,129	971	1,129	971
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	(8)	(15)	(22)	9
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	43	44	44	43
Reported in Net investment gains (losses)	0	0	0	0
Reported in Other comprehensive income (loss)	0	(1)	(1)	0
Total realized and unrealized investment gains (losses)	0	(1)	(1)	0
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	43	43	43
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	0	(1)	(1)	0
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	871	859	901	788
Reported in Net investment gains (losses)	(3)	(1)	(7)	(1)
Reported in Other comprehensive income (loss)	(11)	(7)	(16)	0
Total realized and unrealized investment gains (losses)	(9)	(3)	(12)	9
Purchases	55	87	73	142
Sales	(5)	0	(14)	0
Settlements	(25)	(17)	(42)	(26)
Transfers into Level 3	0	0	0	23
Transfers out of Level 3	0	(43)	(19)	(53)
Balance, Ending, Assets	887	883	887	883
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	(11)	(7)	(16)	(1)
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	11	29	24	35
Reported in Net investment gains (losses)	0	0	0	0
Reported in Other comprehensive income (loss)	0	0	0	0
Total realized and unrealized investment gains (losses)	0	(1)	6	(7)
Purchases	3	0	3	0
Sales	0	(2)	(19)	(2)
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	14	26	14	26
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	(1)	2	(7)
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	5	4	17	3
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	11	10
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	$ 0	$ (1)	$ 6	$ (7)