Derivative Instruments and Hedging Activities - Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged liability, fair value hedge	$ 6,346	$ 7,750
Hedged Liability, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt
Available-for-sale securities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged asset, fair value hedge	$ 15,815	$ 16,302
Hedged asset, fair value hedge, cumulative increase (decrease)	$ 32	$ (79)
Hedged Asset, Statement of Financial Position [Extensible Enumeration]	Available-for-sale securities (amortized cost of $27,312 and $28,416)	Available-for-sale securities (amortized cost of $27,312 and $28,416)
Closed portfolio and beneficial interest, last-of-layer, amortized cost	$ 14,300	$ 14,800
Amortized cost	14,100	14,600
Basis adjustment for active hedge	50	(45)
Hedged asset, last-of-layer, amount	12,000	11,300
Available-for-sale securities | Total derivatives designated as accounting hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Basis adjustment for active hedge	157	75
Finance receivables and loans, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged asset, fair value hedge	39,312	54,189
Hedged asset, fair value hedge, cumulative increase (decrease)	$ 28	$ (93)
Hedged Asset, Statement of Financial Position [Extensible Enumeration]	Finance receivables and loans, net	Finance receivables and loans, net
Basis adjustment for active hedge	$ 28	$ (93)
Hedged asset, last-of-layer, amount	20,800	23,200
Closed portfolio, carrying value	38,000	50,000
Finance receivables and loans, net | Total derivatives designated as accounting hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Basis adjustment for active hedge	41	(66)
Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged liability, fair value hedge, cumulative increase (decrease)	91	100
Discontinued hedge | Available-for-sale securities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged asset, discontinued fair value hedge, cumulative increase (decrease)	(138)	(156)
Basis adjustment for active hedge	(107)	(120)
Discontinued hedge | Finance receivables and loans, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged asset, discontinued fair value hedge, cumulative increase (decrease)	(13)	(27)
Basis adjustment for active hedge	(13)	(27)
Discontinued hedge | Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Hedged liability, discontinued fair value hedge, cumulative increase (decrease)	$ 91	$ 100