Fair Value - Schedule of Fair Value Measurements - Nonrecurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, net	$ 306	$ 400
Finance receivables and loans, net	133,801	135,852
Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, net	68	375
Lower-of-cost-or-fair-value reserve, valuation reserve, or cumulative adjustments	0	0
Assets | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	131	441
Lower-of-cost-or-fair-value reserve, valuation reserve, or cumulative adjustments	(57)	(43)
Nonmarketable equity investments | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	1	1
Lower-of-cost-or-fair-value reserve, valuation reserve, or cumulative adjustments	(1)	1
Repossessed and foreclosed assets | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	6	10
Lower-of-cost-or-fair-value reserve, valuation reserve, or cumulative adjustments	(1)	(1)
Level 1 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, net	0	0
Level 1 | Assets | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 1 | Nonmarketable equity investments | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
Level 1 | Repossessed and foreclosed assets | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
Level 2 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, net	0	0
Level 2 | Assets | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1	0
Level 2 | Nonmarketable equity investments | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	1	0
Level 2 | Repossessed and foreclosed assets | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	0
Level 3 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held-for-sale, net	68	375
Level 3 | Assets | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	130	441
Level 3 | Nonmarketable equity investments | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	0	1
Level 3 | Repossessed and foreclosed assets | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	6	10
Commercial | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	56	55
Lower-of-cost-or-fair-value reserve, valuation reserve, or cumulative adjustments	(55)	(43)
Commercial | Level 1 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	0	0
Commercial | Level 2 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	0	0
Commercial | Level 3 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	56	55
Automotive | Commercial | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	18	6
Lower-of-cost-or-fair-value reserve, valuation reserve, or cumulative adjustments	(2)	0
Automotive | Commercial | Level 1 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	0	0
Automotive | Commercial | Level 2 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	0	0
Automotive | Commercial | Level 3 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	18	6
Other | Commercial | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	38	49
Lower-of-cost-or-fair-value reserve, valuation reserve, or cumulative adjustments	(53)	(43)
Other | Commercial | Level 1 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	0	0
Other | Commercial | Level 2 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	0	0
Other | Commercial | Level 3 | Nonrecurring fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Finance receivables and loans, net	$ 38	$ 49