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
	Mar. 31, 2023	Mar. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,676	$ 1,578
Reported in Net investment gains (losses)	$ 0	$ 0
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)	$ 32	$ (108)
Total realized and unrealized investment gains (losses)	31	(103)
Purchases	136	219
Sales	0	(5)
Settlements	(12)	(39)
Transfers into Level 3	23	15
Transfers out of Level 3	(10)	(51)
Balance, Ending, Assets	1,844	1,614
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(6)	3
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	32	(108)
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	810	937
Reported in Net investment gains (losses)	0	(1)
Reported in Other comprehensive income (loss)	24	(71)
Total realized and unrealized investment gains (losses)	24	(72)
Purchases	81	67
Sales	0	(5)
Settlements	(3)	(22)
Transfers into Level 3	0	10
Transfers out of Level 3	0	0
Balance, Ending, Assets	912	915
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	24	(72)
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	43	56
Reported in Net investment gains (losses)	0	0
Reported in Other comprehensive income (loss)	1	(5)
Total realized and unrealized investment gains (losses)	1	(5)
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	44	51
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	1	(5)
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	788	556
Reported in Net investment gains (losses)	0	2
Reported in Other comprehensive income (loss)	7	(32)
Total realized and unrealized investment gains (losses)	12	(29)
Purchases	55	140
Sales	0	0
Settlements	(9)	(17)
Transfers into Level 3	23	5
Transfers out of Level 3	(10)	(51)
Balance, Ending, Assets	859	604
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	7	(31)
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	35	29
Reported in Net investment gains (losses)	0	(1)
Reported in Other comprehensive income (loss)	0	0
Total realized and unrealized investment gains (losses)	(6)	3
Purchases	0	12
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	29	44
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(6)	3
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	(1)	5
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	5	1
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	$ (6)	$ 4