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		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,614	$ 1,155	$ 1,578	$ 1,151
Reported in Other comprehensive income (loss)	(139)	22	(247)	(29)
Total realized and unrealized investment gains (losses)	(135)	26	(238)	(34)
Purchases	143	218	362	290
Sales	(5)	(7)	(10)	(7)
Settlements	(51)	(33)	(90)	(52)
Transfers into Level 3	14	21	29	40
Transfers out of Level 3	0	(5)	(51)	(13)
Balance, Ending, Assets	1,580	1,375	1,580	1,375
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(3)	0	(1)	2
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Other comprehensive income (loss) in the period	(138)	22	(246)	(29)
Corporate and other bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	915	767	937	770
Reported in Other comprehensive income (loss)	(82)	16	(153)	(24)
Total realized and unrealized investment gains (losses)	(83)	19	(155)	(34)
Purchases	51	122	118	164
Sales	0	(3)	(5)	(3)
Settlements	(37)	(22)	(59)	(24)
Transfers into Level 3	0	0	10	10
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	846	883	846	883
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	(81)	16	(153)	(24)
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	51	44	56	46
Reported in Other comprehensive income (loss)	(5)	2	(10)	0
Total realized and unrealized investment gains (losses)	(5)	2	(10)	0
Purchases	0	12	0	12
Sales	0	0	0	0
Settlements	0	(1)	0	(1)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	46	57	46	57
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	(5)	2	(10)	0
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	604	315	556	308
Reported in Other comprehensive income (loss)		4	(84)	(5)
Total realized and unrealized investment gains (losses)	(44)	5	(73)	(2)
Purchases	92	84	232	114
Sales	(2)	0	(2)	0
Settlements	(23)	(10)	(40)	(27)
Transfers into Level 3	14	21	19	30
Transfers out of Level 3	0	(5)	(51)	(13)
Balance, Ending, Assets	641	410	641	410
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	(52)	4	(83)	(5)
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	44	29	29	27
Reported in Other comprehensive income (loss)	0	0	0	0
Total realized and unrealized investment gains (losses)	(3)	0	0	2
Purchases	0	0	12	0
Sales	(3)	(4)	(3)	(4)
Settlements	9	0	9	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	47	25	47	25
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) in the period	(3)	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 gains (losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment gains (losses)	0	3	0	(9)
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)	(1)	3	(2)	(10)
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	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)	3	0	5	0
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)	0	(3)	1
Reported in Net investment income
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Reported in Net investment income	4	1	9	4
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	1	6	3
Reported in Other comprehensive income (loss)	(52)
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)	$ 0	$ 3	$ 1