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, 2021	Dec. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,151	$ 651
Reported in Other comprehensive income (loss)	(43)	60
Total realized and unrealized investment gains (losses)	(46)	56
Purchases	612	478
Sales	(32)	(12)
Settlements	(130)	(45)
Transfers into Level 3	150	40
Transfers out of Level 3	(127)	(17)
Balance, Ending, Assets	1,578	1,151
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(2)	(6)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(44)	62
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	770	468
Reported in Other comprehensive income (loss)	(32)	43
Total realized and unrealized investment gains (losses)	(42)	44
Purchases	312	264
Sales	(3)	(3)
Settlements	(68)	(13)
Transfers into Level 3	20	10
Transfers out of Level 3	(52)	0
Balance, Ending, Assets	937	770
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	(32)	43
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	46	0
Reported in Other comprehensive income (loss)	(1)	1
Total realized and unrealized investment gains (losses)	(1)	1
Purchases	12	45
Sales	0	0
Settlements	(1)	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	56	46
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)	1
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	308	165
Reported in Other comprehensive income (loss)	(10)	16
Total realized and unrealized investment gains (losses)	(3)	17
Purchases	287	154
Sales	(9)	(9)
Settlements	(61)	(32)
Transfers into Level 3	109	30
Transfers out of Level 3	(75)	(17)
Balance, Ending, Assets	556	308
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	(11)	18
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	27	18
Reported in Other comprehensive income (loss)	0	0
Total realized and unrealized investment gains (losses)	0	(6)
Purchases	1	15
Sales	(20)	0
Settlements	0	0
Transfers into Level 3	21	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	29	27
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(2)	(6)
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	0	0
Reported in Net investment gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment gains (losses)	(12)	(4)
Reported in Net investment gains (losses) | Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment gains (losses)	(10)	1
Reported in Net investment gains (losses) | States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment gains (losses)	0	0
Reported in Net investment gains (losses) | Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment gains (losses)	0	(1)
Reported in Net investment gains (losses) | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment gains (losses)	(2)	(4)
Reported in Net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment income	9	0
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	7	2
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	$ 2	$ (2)