Reinsurance (Effects of Reinsurance on Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets
Premiums, reinsurance and other receivables relating to variable interest entities	$ 17,870	$ 20,443
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	16,389	17,833	$ 18,895
Total assets	34,259	38,276
Liabilities
Future policy benefits	206,656	194,909
Policyholder account balances	205,176	192,627
Other policy-related balances	17,101	17,171
Other liabilities	23,614	24,179
Total liabilities	452,547	428,886
Direct Reinsurance [Member]
Assets
Premiums, reinsurance and other receivables relating to variable interest entities	5,032	6,814
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	16,482	17,822
Total assets	21,514	24,636
Liabilities
Future policy benefits	203,000	191,403
Policyholder account balances	204,906	192,328
Other policy-related balances	15,769	15,806
Other liabilities	16,283	16,165
Total liabilities	439,958	415,702
Assumed Reinsurance [Member]
Assets
Premiums, reinsurance and other receivables relating to variable interest entities	2,107	2,190
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	230	301
Total assets	2,337	2,491
Liabilities
Future policy benefits	3,656	3,506
Policyholder account balances	270	299
Other policy-related balances	1,332	1,351
Other liabilities	2,417	2,402
Total liabilities	7,675	7,558
Ceded Reinsurance [Member]
Assets
Premiums, reinsurance and other receivables relating to variable interest entities	10,731	11,439
Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net	(323)	(290)
Total assets	10,408	11,149
Liabilities
Future policy benefits	0	0
Policyholder account balances	0	0
Other policy-related balances	0	14
Other liabilities	4,914	5,612
Total liabilities	$ 4,914	$ 5,626