Derivatives and Hedging Activities - Deferred Premium, Options and Swaptions (Details) $ in Millions	Sep. 30, 2021 USD ($)
Summary of Option Premiums Payable and Receivable
Premiums payable	$ 840
Premiums receivable	428
2021
Summary of Option Premiums Payable and Receivable
Premiums payable	60	[1]
Premiums receivable	45	[1]
2022
Summary of Option Premiums Payable and Receivable
Premiums payable	204
Premiums receivable	205
2023
Summary of Option Premiums Payable and Receivable
Premiums payable	51
Premiums receivable	43
2024
Summary of Option Premiums Payable and Receivable
Premiums payable	138
Premiums receivable	25
2025
Summary of Option Premiums Payable and Receivable
Premiums payable	125
Premiums receivable	22
2026-2028
Summary of Option Premiums Payable and Receivable
Premiums payable	262
Premiums receivable	$ 88

[1] 2021 amounts represent the amounts payable and receivable for the period from October 1, 2021 to December 31, 2021.