Derivatives and Hedging Activities (Option Pay/Rec) (Details 3) $ in Millions	Dec. 31, 2019 USD ($)
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	$ 1,117
Premiums receivable	518
2020 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	214
Premiums receivable	133
2021 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	152
Premiums receivable	112
2022 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	204
Premiums receivable	198
2023 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	126
Premiums receivable	58
2024 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	70
Premiums receivable	10
2025-2029 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	351
Premiums receivable	$ 7