Derivative Financial Instruments - Carrying Amount and Cumulative Basis Adjustments for Hedge Accounting (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivatives designated as hedging instruments | Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Assets	$ 12,463	$ 12,513
Active	(340)	(644)
Derivatives designated as hedging instruments | Total available-for-sale investment securities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Assets	11,260	9,801
Active	(503)	(675)
Derivatives designated as hedging instruments | Total available-for-sale investment securities | Closed Portfolio
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Assets	685	207
Active	(6)	(4)
Last-of-layer, amount	400	64
Derivatives not designated as hedging instruments | Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Assets	156	362
Derivatives not designated as hedging instruments | Total available-for-sale investment securities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Assets	$ 3	$ 8