Derivatives and Hedging Activites (Option Pay/Rec) (Details 3) $ in Millions	Sep. 30, 2019 USD ($)
Summary of Option Premiums Payable and Receivable
Premiums payable	$ 1,359
Premiums receivable	605
2019 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	141	[1]
Premiums receivable	98	[1]
2020 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	232
Premiums receivable	134
2021 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	186
Premiums receivable	113
2022 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	221
Premiums receivable	200
2023 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	142
Premiums receivable	43
2024-2028 [Member]
Summary of Option Premiums Payable and Receivable
Premiums payable	437
Premiums receivable	$ 17

[1] 2019 amounts represent the amounts payable and receivable for the period from October 1, 2019 to December 31, 2019.