Debt - Interest Expense and LT Debt Maturities (Details) - USD ($) $ in Millions	1 Months Ended				9 Months Ended
	Oct. 31, 2020	Sep. 30, 2020	May 31, 2020	Apr. 30, 2020	Sep. 30, 2020
Debt Instrument [Line Items]
2020 (October 1, 2020 to December 31, 2020)		$ 11,095			$ 11,095
2021		29,618			29,618
2022		17,311			17,311
2023		25,257			25,257
2024		7,037			7,037
2025		8,865			8,865
Thereafter		18,436			18,436
Total		117,619			$ 117,619
Unsecured Debt [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Repayments of lines of credit		2,000
Debt term			3 years	3 years
Aggregate borrowing capacity			$ 2,000	$ 3,000
Unsecured Debt [Member] | Five Year Revolving Credit Facility Due 2023 [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Debt term					5 years
Aggregate borrowing capacity		10,500			$ 10,500
Unsecured Debt [Member] | Five Year Revolving Credit Facility Due 2023 [Member] | Line of Credit [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of lines of credit	$ 3,900
Debt term	5 years
Aggregate borrowing capacity	$ 10,500
Automotive [Member]
Debt Instrument [Line Items]
2020 (October 1, 2020 to December 31, 2020)		526			526
2021		1,783			1,783
2022		113			113
2023		13,002			13,002
2024		71			71
2025		2,558			2,558
Thereafter		11,203			11,203
Total		29,256			29,256
GM Financial [Member]
Debt Instrument [Line Items]
2020 (October 1, 2020 to December 31, 2020)		10,569			10,569
2021		27,835			27,835
2022		17,198			17,198
2023		12,255			12,255
2024		6,966			6,966
2025		6,307			6,307
Thereafter		7,233			7,233
Total		88,363			88,363
GM Financial [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Aggregate borrowing capacity		$ 17,300			$ 17,300