Investments (Securities Pledged) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total securities pledged	$ 18,724	$ 18,405
Total liabilities supported by the pledged collateral	16,518	16,746
Fixed maturities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total securities pledged	15,109	15,319
Assets supporting experience-rated contractholder liabilities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total securities pledged	22	123
Separate account assets
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total securities pledged	2,547	2,811
Equity securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total securities pledged	543	152
Securities sold under agreements to repurchase
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total liabilities supported by the pledged collateral	9,681	9,950
Cash collateral for loaned securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total liabilities supported by the pledged collateral	4,213	3,929
Separate account liabilities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total liabilities supported by the pledged collateral	2,624	2,867
Other
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total securities pledged	445	0
Trading | Fixed maturities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total securities pledged	$ 58	$ 0