Fair Value Measurements - Changes in balances of Level 3 financial assets carried at fair value (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	$ 3,706	$ 3,841
Total realized/unrealized gains (losses) included in Net income	126	(43)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(45)	(48)
Purchases and issuances	351	202
Sales and settlements	(247)	(223)
Transfer into Level 3	51	195
Transfer out of Level 3	(293)	(411)
Financial assets, Ending Balance	3,649	3,513
Fixed maturities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	538	571
Total realized/unrealized gains (losses) included in Net income	(1)	(6)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(2)	(4)
Purchases and issuances	142	46
Sales and settlements	(42)	(49)
Transfer into Level 3	19	53
Transfer out of Level 3	(52)	(66)
Financial assets, Ending Balance	602	545
U.S. government agency
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	0	0
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	0	0
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	0
Financial assets, Ending Balance	0	0
State and municipal
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	39	40
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	1
Purchases and issuances	0	0
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	0
Financial assets, Ending Balance	39	41
Residential MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	38	45
Total realized/unrealized gains (losses) included in Net income	(3)	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	(2)
Purchases and issuances	6	0
Sales and settlements	0	(1)
Transfer into Level 3	3	1
Transfer out of Level 3	(17)	0
Financial assets, Ending Balance	27	44
Commercial MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	2	6
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	0	0
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	(2)	0
Financial assets, Ending Balance	0	6
Collateralized loan obligations
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	16	1
Total realized/unrealized gains (losses) included in Net income	1	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)	0
Purchases and issuances	0	0
Sales and settlements	(1)	0
Transfer into Level 3	0	43
Transfer out of Level 3	(9)	0
Financial assets, Ending Balance	6	44
Other asset-backed securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	305	256
Total realized/unrealized gains (losses) included in Net income	0	(6)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	52	22
Sales and settlements	(23)	(41)
Transfer into Level 3	14	7
Transfer out of Level 3	(22)	0
Financial assets, Ending Balance	326	238
Corporate and other
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	138	223
Total realized/unrealized gains (losses) included in Net income	1	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)	(3)
Purchases and issuances	84	24
Sales and settlements	(18)	(7)
Transfer into Level 3	2	2
Transfer out of Level 3	(2)	(66)
Financial assets, Ending Balance	204	172
Equity securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	176	161
Total realized/unrealized gains (losses) included in Net income	53	(18)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	12	3
Sales and settlements	(14)	0
Transfer into Level 3	0	9
Transfer out of Level 3	0	0
Financial assets, Ending Balance	227	155
Assets of MIE
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	21	17
Total realized/unrealized gains (losses) included in Net income	4	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	1	0
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	(12)	0
Financial assets, Ending Balance	14	16
Assets of discontinued annuity operations | Annuity subsidiaries
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	2,971	3,092
Total realized/unrealized gains (losses) included in Net income	70	(18)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(43)	(44)
Purchases and issuances	196	153
Sales and settlements	(191)	(174)
Transfer into Level 3	32	133
Transfer out of Level 3	(229)	(345)
Financial assets, Ending Balance	$ 2,806	$ 2,797