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		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 2,073	$ 1,923	$ 2,014	$ 1,676
Reported in Net investment gains (losses)	(3)	(4)	$ (10)	$ (5)
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)	91	(66)	$ 54	$ (57)
Total realized and unrealized investment gains (losses)	92	(66)	65	(55)
Purchases	121	90	343	381
Sales	(10)	(2)	(43)	(4)
Settlements	(47)	(32)	(142)	(66)
Transfers into Level 3	0	0	11	34
Transfers out of Level 3	(18)	(7)	(37)	(60)
Balance, Ending, Assets	2,211	1,906	2,211	1,906
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	(1)	2	(8)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	89	(66)	49	(57)
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,129	971	1,045	810
Reported in Net investment gains (losses)	0	0	0	0
Reported in Other comprehensive income (loss)	59	(36)	39	(27)
Total realized and unrealized investment gains (losses)	59	(36)	39	(27)
Purchases	83	29	229	178
Sales	(10)	0	(10)	0
Settlements	(24)	(19)	(77)	(27)
Transfers into Level 3	0	0	11	11
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	1,237	945	1,237	945
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	57	(36)	34	(27)
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	43	43	44	43
Reported in Net investment gains (losses)	0	0	0	0
Reported in Other comprehensive income (loss)	2	(2)	1	(2)
Total realized and unrealized investment gains (losses)	2	(2)	1	(2)
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	45	41	45	41
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	2	(2)	1	(2)
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	887	883	901	788
Reported in Net investment gains (losses)	(3)	(4)	(10)	(5)
Reported in Other comprehensive income (loss)	30	(28)	14	(28)
Total realized and unrealized investment gains (losses)	31	(27)	19	(18)
Purchases	38	61	111	203
Sales	0	0	(14)	0
Settlements	(23)	(13)	(65)	(39)
Transfers into Level 3	0	0	0	23
Transfers out of Level 3	(18)	(7)	(37)	(60)
Balance, Ending, Assets	915	897	915	897
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	30	(28)	14	(28)
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	14	26	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	(8)
Purchases	0	0	3	0
Sales	0	(2)	(19)	(4)
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	23	14	23
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	(1)	2	(8)
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	21	7
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	4	5	15	15
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	$ (8)