Fair Value Measurements - Changes in balances of Level 3 financial assets carried at fair value (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	May 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		$ 865	$ 3,840	$ 3,706	$ 3,841
Total realized/unrealized gains (losses) included in Net income		5	(13)	161	(58)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		(1)	23	(23)	47
Purchases and issuances		98	104	535	569
Sales and settlements		(52)	(159)	(496)	(432)
Transfer into Level 3		10	247	66	598
Transfer out of Level 3		(27)	(237)	(332)	(760)
Sale of annuity business	$ (2,719)
Financial assets, Ending Balance		898	3,805	898	3,805
Fixed maturities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		605	615	538	571
Total realized/unrealized gains (losses) included in Net income		0	1	(3)	(5)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		(1)	4	(2)	8
Purchases and issuances		77	16	279	109
Sales and settlements		(48)	(46)	(145)	(107)
Transfer into Level 3		10	23	33	105
Transfer out of Level 3		(25)	(39)	(82)	(107)
Sale of annuity business	0
Financial assets, Ending Balance		618	574	618	574
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		36	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	0	0	2
Purchases and issuances		0	0	0	0
Sales and settlements		0	0	(3)	(1)
Transfer into Level 3		8	0	8	0
Transfer out of Level 3		(2)	0	(2)	0
Sale of annuity business	0
Financial assets, Ending Balance		42	41	42	41
Residential MBS
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		28	42	38	45
Total realized/unrealized gains (losses) included in Net income		(1)	(1)	(4)	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0	(1)
Purchases and issuances		0	0	6	0
Sales and settlements		(1)	(3)	(2)	(5)
Transfer into Level 3		0	8	6	9
Transfer out of Level 3		(8)	(1)	(26)	(3)
Sale of annuity business	0
Financial assets, Ending Balance		18	45	18	45
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	(4)	(2)	(4)
Sale of annuity business	0
Financial assets, Ending Balance		0	2	0	2
Collateralized loan obligations
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		6	55	16	1
Total realized/unrealized gains (losses) included in Net income		0	0	1	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		1	1	0	4
Purchases and issuances		0	0	0	0
Sales and settlements		0	0	(1)	0
Transfer into Level 3		0	0	0	52
Transfer out of Level 3		(6)	0	(15)	0
Sale of annuity business	0
Financial assets, Ending Balance		1	56	1	56
Other asset-backed securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		315	293	305	256
Total realized/unrealized gains (losses) included in Net income		1	(1)	1	(6)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		(1)	2	0	3
Purchases and issuances		41	8	131	69
Sales and settlements		(38)	(15)	(110)	(62)
Transfer into Level 3		0	14	14	41
Transfer out of Level 3		(9)	(8)	(32)	(8)
Sale of annuity business	0
Financial assets, Ending Balance		309	293	309	293
Corporate and other
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		220	178	138	223
Total realized/unrealized gains (losses) included in Net income		0	3	(1)	2
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		(1)	1	(2)	0
Purchases and issuances		36	8	142	40
Sales and settlements		(9)	(28)	(29)	(39)
Transfer into Level 3		2	1	5	3
Transfer out of Level 3		0	(26)	(5)	(92)
Sale of annuity business	0
Financial assets, Ending Balance		248	137	248	137
Equity securities
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		245	164	176	161
Total realized/unrealized gains (losses) included in Net income		7	(5)	78	(22)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0	0
Purchases and issuances		20	5	44	16
Sales and settlements		(4)	0	(23)	0
Transfer into Level 3		0	0	0	9
Transfer out of Level 3		0	(5)	(7)	(5)
Sale of annuity business	0
Financial assets, Ending Balance		268	159	268	159
Assets of MIE
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance		15	17	21	17
Total realized/unrealized gains (losses) included in Net income		(2)	(2)	1	(4)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)		0	0	0	0
Purchases and issuances		1	0	3	0
Sales and settlements		0	0	0	0
Transfer into Level 3		0	0	1	2
Transfer out of Level 3		(2)	0	(14)	0
Sale of annuity business	0
Financial assets, Ending Balance		12	15	12	15
Assets of discontinued annuity operations | Annuity subsidiaries
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance			3,044	2,971	3,092
Total realized/unrealized gains (losses) included in Net income			(7)	85	(27)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)			19	(21)	39
Purchases and issuances			83	209	444
Sales and settlements			(113)	(328)	(325)
Transfer into Level 3			224	32	482
Transfer out of Level 3			(193)	(229)	(648)
Sale of annuity business	$ (2,719)
Financial assets, Ending Balance		$ 0	$ 3,057	$ 0	$ 3,057