Related Party Transactions - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Mar. 31, 2023	Feb. 28, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Related Party Transaction [Line Items]
Revenues			$ 3,641,000,000	$ 3,187,000,000	$ 10,481,000,000	$ 9,489,000,000
Related party tax payment					$ 67,000,000	508,000,000
Line of Credit | General Motors | Five Year Revolving Credit Facility
Related Party Transaction [Line Items]
Maximum borrowing capacity		$ 11,200,000,000
Debt instrument term		5 years			5 years
Current borrowing capacity	$ 10,000,000,000		10,000,000,000		$ 10,000,000,000
Line of Credit | General Motors | 364 Day Revolving Credit Facilities
Related Party Transaction [Line Items]
Debt instrument term	364 days
Revolving Credit Facility
Related Party Transaction [Line Items]
Maximum borrowing capacity			17,700,000,000		17,700,000,000
Revolving Credit Facility | Line of Credit | Cruise
Related Party Transaction [Line Items]
Long-term line of credit			276,000,000		276,000,000		$ 113,000,000
Maximum borrowing capacity			4,300,000,000		4,300,000,000
Revolving Credit Facility | Line of Credit | General Motors
Related Party Transaction [Line Items]
Maximum borrowing capacity			14,100,000,000		$ 14,100,000,000
Revolving Credit Facility | Line of Credit | General Motors | Three Year Revolving Credit Facility
Related Party Transaction [Line Items]
Maximum borrowing capacity		$ 4,300,000,000
Debt instrument term		3 years			3 years
Current borrowing capacity	$ 4,100,000,000		4,100,000,000		$ 4,100,000,000
Revolving Credit Facility | Line of Credit | General Motors | 364 Day Revolving Credit Facilities
Related Party Transaction [Line Items]
Maximum borrowing capacity			2,000,000,000		$ 2,000,000,000
Debt instrument term					364 days
Junior Subordinated Revolving Credit Facility | General Motors
Related Party Transaction [Line Items]
Line of credit facilities - GM Related party facility			1,000,000,000		$ 1,000,000,000
GM
Related Party Transaction [Line Items]
Revenues			$ 629,000,000	$ 732,000,000	$ 2,300,000,000	$ 1,700,000,000