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, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,923	$ 1,580	$ 1,676	$ 1,578
Reported in Net investment gains (losses)	$ (4)	$ (1)	$ (5)	$ (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	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 loss	Other comprehensive loss	Other comprehensive loss	Other comprehensive loss
Reported in Other comprehensive income (loss)	$ (66)	$ (92)	$ (57)	$ (339)
Total realized and unrealized investment gains (losses)	(66)	(91)	(55)	(329)
Purchases	90	125	381	487
Sales	(2)	0	(4)	(10)
Settlements	(32)	(18)	(66)	(108)
Transfers into Level 3	0	47	34	76
Transfers out of Level 3	(7)	(53)	(60)	(104)
Balance, Ending, Assets	1,906	1,590	1,906	1,590
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(1)	(7)	(8)	(8)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(66)	(93)	(57)	(338)
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	971	846	810	937
Reported in Net investment gains (losses)	0	0	0	(2)
Reported in Other comprehensive income (loss)	(36)	(50)	(27)	(203)
Total realized and unrealized investment gains (losses)	(36)	(49)	(27)	(204)
Purchases	29	9	178	127
Sales	0	0	0	(5)
Settlements	(19)	(4)	(27)	(63)
Transfers into Level 3	0	0	11	10
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	945	802	945	802
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	(36)	(51)	(27)	(203)
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	43	46	43	56
Reported in Net investment gains (losses)	0	0	0	0
Reported in Other comprehensive income (loss)	(2)	(4)	(2)	(14)
Total realized and unrealized investment gains (losses)	(2)	(4)	(2)	(14)
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	41	42	41	42
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)	(4)	(2)	(14)
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	883	641	788	556
Reported in Net investment gains (losses)	(4)	2	(5)	7
Reported in Other comprehensive income (loss)	(28)	(38)	(28)	(122)
Total realized and unrealized investment gains (losses)	(27)	(31)	(18)	(104)
Purchases	61	116	203	348
Sales	0	0	0	(2)
Settlements	(13)	(14)	(39)	(54)
Transfers into Level 3	0	47	23	66
Transfers out of Level 3	(7)	(43)	(60)	(94)
Balance, Ending, Assets	897	716	897	716
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	(28)	(38)	(28)	(121)
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	26	47	35	29
Reported in Net investment gains (losses)	0	(3)	0	(6)
Reported in Other comprehensive income (loss)	0	0	0	0
Total realized and unrealized investment gains (losses)	(1)	(7)	(8)	(7)
Purchases	0	0	0	12
Sales	(2)	0	(4)	(3)
Settlements	0	0	0	9
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(10)	0	(10)
Balance, Ending, Assets	23	30	23	30
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(1)	(7)	(8)	(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	2	7	11
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	1	0	1
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	15	11
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)	$ (4)	$ (8)	$ (1)