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	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 2,014	$ 1,676
Reported in Net investment gains (losses)	$ (13)	$ (4)
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)	$ (29)	$ 48
Total realized and unrealized investment gains (losses)	(9)	57
Purchases	480	467
Sales	(43)	(4)
Settlements	(187)	(97)
Transfers into Level 3	11	34
Transfers out of Level 3	(50)	(119)
Balance, Ending, Assets	2,216	2,014
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	7	(7)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(35)	48
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,045	810
Reported in Net investment gains (losses)	(1)	0
Reported in Other comprehensive income (loss)	(15)	38
Total realized and unrealized investment gains (losses)	(16)	38
Purchases	352	219
Sales	(10)	0
Settlements	(104)	(33)
Transfers into Level 3	11	11
Transfers out of Level 3	0	0
Balance, Ending, Assets	1,278	1,045
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(1)	0
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(21)	38
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	44	43
Reported in Net investment gains (losses)	0	0
Reported in Other comprehensive income (loss)	(2)	1
Total realized and unrealized investment gains (losses)	(2)	1
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	42	44
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	0
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(2)	1
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	901	788
Reported in Net investment gains (losses)	(12)	(4)
Reported in Other comprehensive income (loss)	(12)	9
Total realized and unrealized investment gains (losses)	(3)	25
Purchases	125	248
Sales	(14)	0
Settlements	(83)	(64)
Transfers into Level 3	0	23
Transfers out of Level 3	(50)	(119)
Balance, Ending, Assets	876	901
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	0	0
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(12)	9
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	24	35
Reported in Net investment gains (losses)	0	0
Reported in Other comprehensive income (loss)	0	0
Total realized and unrealized investment gains (losses)	12	(7)
Purchases	3	0
Sales	(19)	(4)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	20	24
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	8	(7)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	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	33	13
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
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
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	21	20
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	$ 12	$ (7)