Schedule IV - Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Life insurance in force, Gross	$ 648,765	$ 686,814	$ 690,790
Life insurance in force, Ceded	245,164	256,619	258,456
Life insurance in force, Assumed	8,377	9,034	7,750
Life insurance in force, Net	$ 411,978	$ 439,229	$ 440,084
Percentage of Assumed to Net, Life insurance in force	2.00%	2.10%	1.80%
Direct premiums	$ 2,759	$ 2,602	$ 2,597
Ceded Premiums	1,313	1,426	1,652
Assumed premiums	827	956	1,152
Net premiums	$ 2,273	$ 2,132	$ 2,097
Percentage Assumed to Net, Premiums	36.40%	44.80%	54.90%
Individual and group life insurance contracts
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct premiums	$ 1,246	$ 1,262	$ 1,271
Ceded Premiums	1,151	1,288	1,510
Assumed premiums	826	955	1,151
Net premiums	$ 921	$ 929	$ 912
Percentage Assumed to Net, Premiums	89.70%	102.80%	126.20%
Accident and health
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct premiums	$ 1,452	$ 1,275	$ 1,051
Ceded Premiums	162	138	142
Assumed premiums	1	1	1
Net premiums	$ 1,291	$ 1,138	$ 910
Percentage Assumed to Net, Premiums	0.10%	0.10%	0.10%
Annuity Contracts
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct premiums	$ 61	$ 65	$ 275
Ceded Premiums	0	0	0
Assumed premiums	0	0	0
Net premiums	$ 61	$ 65	$ 275
Percentage Assumed to Net, Premiums	0.00%	0.00%	0.00%