Reserve for Life-Contingent Contract Benefits and Contractholder Funds - Contractholder funds (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Key contract provisions relating to contractholder funds:
Total contractholder funds	$ 17,213	$ 17,692	$ 18,371	$ 19,434
Interest-sensitive life insurance contract charges
Key contract provisions relating to contractholder funds:
Total contractholder funds	8,493	8,384
Fixed annuities contract charges
Key contract provisions relating to contractholder funds:
Total contractholder funds	8,196	8,845
Other investment contracts
Key contract provisions relating to contractholder funds:
Total contractholder funds	$ 524	$ 463
Other investment contracts | Minimum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	1.70%
Other investment contracts | Maximum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	10.30%
Equity indexed life insurance | Minimum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	0.00%
Equity indexed life insurance | Maximum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	9.00%
Other life insurance | Minimum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	1.00%
Other life insurance | Maximum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	6.00%
Immediate fixed annuities | Minimum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	0.50%
Immediate fixed annuities | Maximum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	7.50%
Equity indexed fixed annuities | Minimum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	(8.00%)
Equity indexed fixed annuities | Maximum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	9.00%
Other fixed annuities | Minimum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	0.10%
Other fixed annuities | Maximum
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)	5.00%