Consolidated Reinsurance (Consolidated Reinsurance) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums, Life Insurance in Force	$ 4,594,523	$ 4,098,780	$ 4,080,869
Ceded Premiums, Life Insurance in Force	513,091	481,028	546,122
Assumed Premiums, Life Insurance in Force	581,246	613,693	593,722
Premiums, Net, Life Insurance in Force	$ 4,662,678	$ 4,231,445	$ 4,128,469
Life Insurance in Force Premiums, Percentage Assumed to Net	12.50%	14.50%	14.40%
Consolidated Reinsurance
Gross Amount	$ 39,595	$ 37,975	$ 37,044
Ceded	2,376	2,136	2,023
Assumed	1,773	1,363	1,382
Premiums	$ 38,992	$ 37,202	$ 36,403
% Amount Assumed to Net	4.50%	3.70%	3.80%
Life insurance (1)
Consolidated Reinsurance
Gross Amount	$ 22,379	$ 20,857	$ 20,854
Ceded	1,863	1,614	1,570
Assumed	1,531	1,089	1,150
Premiums	$ 22,047	$ 20,332	$ 20,434
% Amount Assumed to Net	6.90%	5.40%	5.60%
Accident & health insurance
Consolidated Reinsurance
Gross Amount	$ 13,593	$ 13,551	$ 12,677
Ceded	442	447	377
Assumed	223	257	219
Premiums	$ 13,374	$ 13,361	$ 12,519
% Amount Assumed to Net	1.70%	1.90%	1.70%
Property & casualty insurance
Consolidated Reinsurance
Gross Amount	$ 3,623	$ 3,567	$ 3,513
Ceded	71	75	76
Assumed	19	17	13
Premiums	$ 3,571	$ 3,509	$ 3,450
% Amount Assumed to Net	0.50%	0.50%	0.40%