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, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 2,328	$ 2,073	$ 2,216	$ 2,014
Reported in Net investment gains (losses)	$ 3	$ (3)	$ 2	$ (10)
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	Other comprehensive income	Other comprehensive income	Other comprehensive income
Reported in Other comprehensive income (loss)	$ 29	$ 91	$ 65	$ 54
Total realized and unrealized investment gains (losses)	37	92	80	65
Purchases	117	121	265	343
Sales	0	(10)	(7)	(43)
Settlements	(69)	(47)	(156)	(142)
Transfers into Level 3	0	0	15	11
Transfers out of Level 3	0	(18)	0	(37)
Balance, Ending, Assets	2,413	2,211	2,413	2,211
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	0	(1)	2
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	30	89	63	49
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,388	1,129	1,278	1,045
Reported in Net investment gains (losses)	0	0	1	0
Reported in Other comprehensive income (loss)	21	59	58	39
Total realized and unrealized investment gains (losses)	21	59	59	39
Purchases	24	83	123	229
Sales	0	(10)	0	(10)
Settlements	(33)	(24)	(75)	(77)
Transfers into Level 3	0	0	15	11
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	1,400	1,237	1,400	1,237
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	21	57	55	34
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	44	43	42	44
Reported in Net investment gains (losses)	0	0	0	0
Reported in Other comprehensive income (loss)	0	2	2	1
Total realized and unrealized investment gains (losses)	0	2	2	1
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	44	45	44	45
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	2	2	1
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	886	887	876	901
Reported in Net investment gains (losses)	3	(3)	(1)	(10)
Reported in Other comprehensive income (loss)	8	30	5	14
Total realized and unrealized investment gains (losses)	16	31	18	19
Purchases	93	38	142	111
Sales	0	0	0	(14)
Settlements	(36)	(23)	(77)	(65)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(18)	0	(37)
Balance, Ending, Assets	959	915	959	915
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	9	30	6	14
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	10	14	20	24
Reported in Net investment gains (losses)	0	0	2	0
Reported in Other comprehensive income (loss)	0	0	0	0
Total realized and unrealized investment gains (losses)	0	0	1	6
Purchases	0	0	0	3
Sales	0	0	(7)	(19)
Settlements	0	0	(4)	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	10	14	10	14
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	0	(1)	2
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	13	21
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	4	14	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	$ 0	$ (1)	$ 6