Fair Value Measurements - Changes in balances of Level 3 financial assets carried at fair value (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	May 31, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		$ 3,649	$ 3,513	$ 3,706	$ 3,841
Total realized/unrealized gains (losses) included in Net income		30	(2)	156	(45)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		22	72	(22)	24
Purchases and issuances		86	263	437	465
Sales and settlements		(196)	(50)	(444)	(273)
Transfer into Level 3		5	156	56	351
Transfer out of Level 3		(12)	(112)	(305)	(523)
Sale of annuity business	$ (2,719)
Financial assets, Ending Balance		865	3,840	865	3,840
Fixed maturities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		602	545	538	571
Total realized/unrealized gains (losses) included in Net income		(2)	0	(3)	(6)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		1	8	(1)	4
Purchases and issuances		60	47	202	93
Sales and settlements		(55)	(12)	(97)	(61)
Transfer into Level 3		4	29	23	82
Transfer out of Level 3		(5)	(2)	(57)	(68)
Sale of annuity business	0
Financial assets, Ending Balance		605	615	605	615
U.S. government agency
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		0	0	0	0
Total realized/unrealized gains (losses) included in Net income		0	0	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0	0
Purchases and issuances		0	0	0	0
Sales and settlements		0	0	0	0
Transfer into Level 3		0	0	0	0
Transfer out of Level 3		0	0	0	0
Sale of annuity business	0
Financial assets, Ending Balance		0	0	0	0
State and municipal
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		39	41	39	40
Total realized/unrealized gains (losses) included in Net income		0	0	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	1	0	2
Purchases and issuances		0	0	0	0
Sales and settlements		(3)	(1)	(3)	(1)
Transfer into Level 3		0	0	0	0
Transfer out of Level 3		0	0	0	0
Sale of annuity business	0
Financial assets, Ending Balance		36	41	36	41
Residential MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		27	44	38	45
Total realized/unrealized gains (losses) included in Net income		0	0	(3)	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	1	0	(1)
Purchases and issuances		0	0	6	0
Sales and settlements		(1)	(1)	(1)	(2)
Transfer into Level 3		3	0	6	1
Transfer out of Level 3		(1)	(2)	(18)	(2)
Sale of annuity business	0
Financial assets, Ending Balance		28	42	28	42
Commercial MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		0	6	2	6
Total realized/unrealized gains (losses) included in Net income		0	0	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0	0
Purchases and issuances		0	0	0	0
Sales and settlements		0	0	0	0
Transfer into Level 3		0	0	0	0
Transfer out of Level 3		0	0	(2)	0
Sale of annuity business	0
Financial assets, Ending Balance		0	6	0	6
Collateralized loan obligations
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		6	44	16	1
Total realized/unrealized gains (losses) included in Net income		0	(1)	1	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	3	(1)	3
Purchases and issuances		0	0	0	0
Sales and settlements		0	0	(1)	0
Transfer into Level 3		0	9	0	52
Transfer out of Level 3		0	0	(9)	0
Sale of annuity business	0
Financial assets, Ending Balance		6	55	6	55
Other asset-backed securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		326	238	305	256
Total realized/unrealized gains (losses) included in Net income		0	1	0	(5)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		1	1	1	1
Purchases and issuances		38	39	90	61
Sales and settlements		(49)	(6)	(72)	(47)
Transfer into Level 3		0	20	14	27
Transfer out of Level 3		(1)	0	(23)	0
Sale of annuity business	0
Financial assets, Ending Balance		315	293	315	293
Corporate and other
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		204	172	138	223
Total realized/unrealized gains (losses) included in Net income		(2)	0	(1)	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	2	(1)	(1)
Purchases and issuances		22	8	106	32
Sales and settlements		(2)	(4)	(20)	(11)
Transfer into Level 3		1	0	3	2
Transfer out of Level 3		(3)	0	(5)	(66)
Sale of annuity business	0
Financial assets, Ending Balance		220	178	220	178
Equity securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		227	155	176	161
Total realized/unrealized gains (losses) included in Net income		18	1	71	(17)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0	0
Purchases and issuances		12	8	24	11
Sales and settlements		(5)	0	(19)	0
Transfer into Level 3		0	0	0	9
Transfer out of Level 3		(7)	0	(7)	0
Sale of annuity business	0
Financial assets, Ending Balance		245	164	245	164
Assets of MIE
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		14	16	21	17
Total realized/unrealized gains (losses) included in Net income		(1)	(1)	3	(2)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0	0
Purchases and issuances		1	0	2	0
Sales and settlements		0	0	0	0
Transfer into Level 3		1	2	1	2
Transfer out of Level 3		0	0	(12)	0
Sale of annuity business	0
Financial assets, Ending Balance		15	17	15	17
Assets of discontinued annuity operations | Annuity subsidiaries
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		2,806	2,797	2,971	3,092
Total realized/unrealized gains (losses) included in Net income		15	(2)	85	(20)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		21	64	(21)	20
Purchases and issuances		13	208	209	361
Sales and settlements		(136)	(38)	(328)	(212)
Transfer into Level 3		0	125	32	258
Transfer out of Level 3		0	(110)	(229)	(455)
Sale of annuity business	$ (2,719)
Financial assets, Ending Balance		$ 0	$ 3,044	$ 0	$ 3,044