Revenue Revenue - Disaggregation of Revenue from Contract with Customer by Products and Services (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	$ 156,776
Vehicles, parts, and accessories
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	140,171
Used vehicles
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	2,956
Extended service contracts
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	1,236
Other revenue (a)
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	1,044
Revenues from sales and services
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	145,407
Leasing income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	6,027
Financing income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	5,184
Insurance income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	158
Operating Segments [Member] | Automotive
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	145,653
Operating Segments [Member] | Automotive | Vehicles, parts, and accessories
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	140,171
Operating Segments [Member] | Automotive | Used vehicles
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	2,956
Operating Segments [Member] | Automotive | Extended service contracts
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	1,236
Operating Segments [Member] | Automotive | Other revenue (a)
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	815
Operating Segments [Member] | Automotive | Revenues from sales and services
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	145,178
Operating Segments [Member] | Automotive | Leasing income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	475
Operating Segments [Member] | Automotive | Financing income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | Automotive | Insurance income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | Financial Services
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	11,113
Operating Segments [Member] | Financial Services | Vehicles, parts, and accessories
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | Financial Services | Used vehicles
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | Financial Services | Extended service contracts
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | Financial Services | Other revenue (a)
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	219
Operating Segments [Member] | Financial Services | Revenues from sales and services
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	219
Operating Segments [Member] | Financial Services | Leasing income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	5,552
Operating Segments [Member] | Financial Services | Financing income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	5,184
Operating Segments [Member] | Financial Services | Insurance income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	158
Operating Segments [Member] | All Other
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	10
Operating Segments [Member] | All Other | Vehicles, parts, and accessories
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | All Other | Used vehicles
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | All Other | Extended service contracts
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | All Other | Other revenue (a)
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	10
Operating Segments [Member] | All Other | Revenues from sales and services
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	10
Operating Segments [Member] | All Other | Leasing income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | All Other | Financing income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	0
Operating Segments [Member] | All Other | Insurance income
Disaggregation of Revenue [Line Items]
Revenue, excluding assessed tax	$ 0