Closed Block (Liabilities and Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Closed Block Liabilities
Future policy benefits	$ 38,521	$ 38,758
Other policy-related balances	321	321
Policyholder dividends payable	338	337
Policyholder dividend obligation	1,546	2,969	$ 2,020
Deferred income tax liability	149	130
Other liabilities	271	172
Total closed block liabilities	41,146	42,687
Assets Designated to the Closed Block
Fixed maturity securities available-for-sale, at estimated fair value	25,696	27,186
Equity securities, at estimated fair value	22	24
Mortgage loans	6,559	6,807
Policy loans	4,314	4,355
Real estate and real estate joint ventures	556	559
Other invested assets	471	468
Total investments	37,618	39,399
Cash and cash equivalents	228	0
Accrued investment income	400	402
Premiums, reinsurance and other receivables	79	50
Current income tax recoverable	40	28
Total assets designated to the closed block	38,365	39,879
Excess of closed block liabilities over assets designated to the closed block	2,781	2,808
AOCI:
Unrealized investment gains (losses), net of income tax	2,460	3,524
Unrealized gains (losses) on derivatives, net of income tax	12	23
Allocated to policyholder dividend obligation, net of income tax	(1,221)	(2,346)
Total amounts included in AOCI	1,251	1,201
Maximum future earnings to be recognized from closed block assets and liabilities	$ 4,032	$ 4,009