Derivatives and Hedging Activities (Option Pay/Rec) (Details 3) $ in Millions	Dec. 31, 2020 USD ($)
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	$ 932
Premiums receivable	387
2021 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	153
Premiums receivable	106
2022 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	207
Premiums receivable	205
2023 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	51
Premiums receivable	43
2024 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	141
Premiums receivable	26
2025 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	126
Premiums receivable	7
2026-2028 [Member]
Summary of Option Premiums Payable and Receivable [Line Items]
Premiums payable	254
Premiums receivable	$ 0