Derivatives and Hedging Activities (Option Pay/Rec) (Details) $ in Millions	Jun. 30, 2020 USD ($)
Summary of option premiums payable and receivable
Premiums payable	$ 1,011
Premiums receivable	410
2020 [Member]
Summary of option premiums payable and receivable
Premiums payable	82	[1]
Premiums receivable	26	[1]
2021 [Member]
Summary of option premiums payable and receivable
Premiums payable	152
Premiums receivable	112
2022 [Member]
Summary of option premiums payable and receivable
Premiums payable	203
Premiums receivable	198
2023 [Member]
Summary of option premiums payable and receivable
Premiums payable	126
Premiums receivable	57
2024 [Member]
Summary of option premiums payable and receivable
Premiums payable	71
Premiums receivable	10
2025-2028 [Member]
Summary of option premiums payable and receivable
Premiums payable	377
Premiums receivable	$ 7

[1] 2020 amounts represent the amounts payable and receivable for the period from July 1, 2020 to December 31, 2020.