Reserve for Life-Contingent Contract Benefits and Contractholder Funds - Summary of liabilities for guarantees (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	$ 419	$ 444
Less reinsurance recoverables	133	185
Net balance at beginning of period	286	259
Incurred guarantee benefits	68	30
Paid guarantee benefits	(2)	(3)
Net change	66	27
Net balance at end of period	352	286
Plus reinsurance recoverables	125	133
Balance at end of period	477	419
Variable annuities
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	419	444
Balance at end of period	477	419
Death benefits | Variable annuities
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	78	109
Balance at end of period	67	78
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	21	36
Balance at end of period	24	21
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	18	25
Balance at end of period	18	18
Withdrawal benefits | Variable annuities
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Balance at beginning of period	14	14
Balance at end of period	15	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	288	260
Balance at end of period	353	288
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	293	308
Less reinsurance recoverables	81	111
Net balance at beginning of period	212	197
Incurred guarantee benefits	50	18
Paid guarantee benefits	(2)	(3)
Net change	48	15
Net balance at end of period	260	212
Plus reinsurance recoverables	69	81
Balance at end of period	329	293
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	24	39
Less reinsurance recoverables	20	35
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	23	20
Balance at end of period	27	24
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	102	97
Less reinsurance recoverables	32	39
Net balance at beginning of period	70	58
Incurred guarantee benefits	18	12
Paid guarantee benefits	0	0
Net change	18	12
Net balance at end of period	88	70
Plus reinsurance recoverables	33	32
Balance at end of period	$ 121	$ 102