Reserve for Life-Contingent Contract Benefits and Contractholder Funds - Liabilities for guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Liabilities for guarantees:
Liabilities for Guarantees on Long-Duration Contracts, Incurred Benefits	$ 37	$ 45
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	369	364
Less reinsurance recoverables	146	184
Net balance at beginning of period	223	180
Paid guarantee benefits	(2)	(2)
Net change	35	43
Net balance at end of period	258	223
Plus reinsurance recoverables	185	146
Balance at end of period	443	369
Liability for guarantees related to death benefits and interest-sensitive life products
Liabilities for guarantees:
Liabilities for Guarantees on Long-Duration Contracts, Incurred Benefits	24	33
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	261	244
Less reinsurance recoverables	87	101
Net balance at beginning of period	174	143
Paid guarantee benefits	(2)	(2)
Net change	22	31
Net balance at end of period	196	174
Plus reinsurance recoverables	111	87
Balance at end of period	307	261
Liability for guarantees related to income benefits
Liabilities for guarantees:
Liabilities for Guarantees on Long-Duration Contracts, Incurred Benefits	0	0
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	28	43
Less reinsurance recoverables	25	40
Net balance at beginning of period	3	3
Paid guarantee benefits	0	0
Net change	0	0
Net balance at end of period	3	3
Plus reinsurance recoverables	35	25
Balance at end of period	38	28
Liability for guarantees related to accumulation and withdrawal benefits
Liabilities for guarantees:
Liabilities for Guarantees on Long-Duration Contracts, Incurred Benefits	13	12
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	80	77
Less reinsurance recoverables	34	43
Net balance at beginning of period	46	34
Paid guarantee benefits	0	0
Net change	13	12
Net balance at end of period	59	46
Plus reinsurance recoverables	39	34
Balance at end of period	$ 98	$ 80