Reserve for Life-Contingent Contract Benefits and Contractholder Funds - Summary of liabilities for guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	$ 444	$ 370
Less reinsurance recoverables	185	146
Net balance at beginning of period	259	224
Incurred guarantee benefits	30	37
Paid guarantee benefits	(3)	(2)
Net change	27	35
Net balance at end of period	286	259
Plus reinsurance recoverables	133	185
Balance at end of period	419	444
In the event of death | Variable annuities
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	109	85
Balance at end of period	78	109
At annuitization (includes income benefit guarantees) | Variable annuities
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	36	26
Balance at end of period	21	36
Accumulation at specified dates | Variable annuities
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	25	22
Balance at end of period	18	25
For cumulative periodic withdrawals | Variable annuities
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	14	12
Balance at end of period	14	14
Other Guarantees | Variable annuities
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	260	225
Balance at end of period	288	260
Liability for guarantees related to death benefits and interest-sensitive life products
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	308	262
Less reinsurance recoverables	111	87
Net balance at beginning of period	197	175
Incurred guarantee benefits	18	24
Paid guarantee benefits	(3)	(2)
Net change	15	22
Net balance at end of period	212	197
Plus reinsurance recoverables	81	111
Balance at end of period	293	308
At annuitization (includes income benefit guarantees)
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	39	29
Less reinsurance recoverables	35	25
Net balance at beginning of period	4	4
Incurred guarantee benefits	0	0
Paid guarantee benefits	0	0
Net change	0	0
Net balance at end of period	4	4
Plus reinsurance recoverables	20	35
Balance at end of period	24	39
Liability for guarantees related to accumulation and withdrawal benefits
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	97	79
Less reinsurance recoverables	39	34
Net balance at beginning of period	58	45
Incurred guarantee benefits	12	13
Paid guarantee benefits	0	0
Net change	12	13
Net balance at end of period	70	58
Plus reinsurance recoverables	32	39
Balance at end of period	$ 102	$ 97