Schedule IV - Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Life insurance in force
Gross amount	$ 188,186	$ 167,355	$ 156,486
Ceded to other companies	86,642	90,011	93,326
Assumed from other companies	259,671	275,008	280,644
Net amount	$ 361,215	$ 352,352	$ 343,804
Percentage of amount assumed to net	71.90%	78.00%	81.60%
Premiums and contract charges:
Gross amount	$ 35,115	$ 34,015	$ 32,915
Ceded premium earned	1,274	1,296	1,338
Assumed from other companies	837	863	890
Net amount	$ 34,678	$ 33,582	$ 32,467
Percentage of amount assumed to net	2.40%	2.60%	2.70%
Reinsurance or coinsurance income net of premium ceded	$ 0	$ 0	$ 0
Life insurance
Premiums and contract charges:
Gross amount	936	877	828
Ceded premium earned	276	279	299
Assumed from other companies	787	818	849
Net amount	$ 1,447	$ 1,416	$ 1,378
Percentage of amount assumed to net	54.40%	57.80%	61.60%
Accident and health insurance
Premiums and contract charges:
Gross amount	$ 958	$ 889	$ 813
Ceded premium earned	27	30	33
Assumed from other companies	0	0	0
Net amount	$ 931	$ 859	$ 780
Percentage of amount assumed to net	0.00%	0.00%	0.00%
Property and casualty insurance
Premiums and contract charges:
Gross amount	$ 33,221	$ 32,249	$ 31,274
Ceded premium earned	971	987	1,006
Assumed from other companies	50	45	41
Net amount	$ 32,300	$ 31,307	$ 30,309
Percentage of amount assumed to net	0.20%	0.10%	0.10%