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Significant Accounting Policies (Details) - USD ($) $ in Millions |  | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jan. 01, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Mar. 31, 2018 | Jan. 01, 2018
Cash Equivalents [Abstract] |  |  |  |  |  |
Maximum Maturity Period for Highly Liquid Securities |  | 90 days |  |  |  |
Pension and Other Postretirement Plans [Abstract] |  |  |  |  |  |
Percentage Recognized as Pension Expense in the First Year |  | 60.00% |  |  |  |
Percentage of Pension Expense Recognized in Each of the Next Four Years |  | 10.00% |  |  |  |
Subsequent Period Over Which Pension Return Adjustment Is Amortized |  | 4 years |  |  |  |
Percentage of Non-US Pension Benefit Obligation Related to Canada, United Kingdom and Germany |  | 92.00% |  |  |  |
Income Taxes [Abstract] |  |  |  |  |  |
Valuation Allowance Methodology Number Of Years Utilized |  | 3 years |  |  |  |
Minimum Percentage Threshold To Recognize The Tax Benefit For Uncertain Tax Positions |  | 50.00% |  |  |  |
Foreign Currency Transactions and Translation [Abstract] |  |  |  |  |  |
Foreign currency transaction and remeasurement losses |  | $ 168 | $ 52 | $ 229 |  |
Recently Adopted Accounting Standards and Accounting Standards Not Yet Adopted [Abstract] |  |  |  |  |  |
Adoption of accounting standards (Note 2) |  | (1,144) |  |  |  |
Automotive Selling, General and Administrative Expense [Member] |  |  |  |  |  |
Advertising and Promotion Expenditures [Abstract] |  |  |  |  |  |
Advertising and Promotion Expenditures |  | 4,000 | 4,300 | 4,600 |  |
Automotive Cost of Sales [Member] |  |  |  |  |  |
Research and Development Expenditures [Abstract] |  |  |  |  |  |
Research and Development Expenditures |  | $ 7,800 | $ 7,300 | $ 6,600 |  |
GM Financial [Member] | Minimum [Member] | Vehicles [Member] |  |  |  |  |  |
Equipment on Operating Leases, net [Abstract] |  |  |  |  |  |
Leasing Arrangements, Term of Contract |  | 2 years |  |  |  |
GM Financial [Member] | Maximum [Member] | Vehicles [Member] |  |  |  |  |  |
Equipment on Operating Leases, net [Abstract] |  |  |  |  |  |
Leasing Arrangements, Term of Contract |  | 5 years |  |  |  |
GM Financial [Member] | Retail Finance Receivables [Member] |  |  |  |  |  |
Revenue Recognition [Abstract] |  |  |  |  |  |
Period Past Due Threshold for Suspending Accrual of Finance Charge Income |  | 60 days |  |  |  |
Finance Receivables [Abstract] |  |  |  |  |  |
Period Past Due Threshold for Charge Off of Finance Receivables |  | 120 days |  |  |  |
GM Financial [Member] | Commercial Finance Receivables [Member] |  |  |  |  |  |
Revenue Recognition [Abstract] |  |  |  |  |  |
Period Past Due Threshold for Suspending Accrual of Finance Charge Income |  | 90 days |  |  |  |
Automotive [Member] |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |
Revenue Recognition, Separate and Bundled Services, Term |  | 3 years |  |  |  |
Automotive [Member] | Vehicles [Member] |  |  |  |  |  |
Equipment on Operating Leases, net [Abstract] |  |  |  |  |  |
Leasing Arrangements, Term of Contract |  | 7 months |  |  |  |
Accounting Standards Update 2016-01 [Member] |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |
Adoption of accounting standards (Note 2) |  |  |  |  |  | $ 182
Accounting Standards Update 2017-12 and Accounting Standards Update 2018-02 [Member] |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |
Adoption of accounting standards (Note 2) |  |  |  |  | $ 108 |
Forecast [Member] | Noncancelable Operating Lease Assets [Member] | Accounting Standards Update 2016-02 [Member] |  |  |  |  |  |
Recently Adopted Accounting Standards and Accounting Standards Not Yet Adopted [Abstract] |  |  |  |  |  |
Adoption of accounting standards (Note 2) | $ 1,000 |  |  |  |  |
Forecast [Member] | Noncancelable Operating Lease Obligations [Member] | Accounting Standards Update 2016-02 [Member] |  |  |  |  |  |
Recently Adopted Accounting Standards and Accounting Standards Not Yet Adopted [Abstract] |  |  |  |  |  |
Adoption of accounting standards (Note 2) | $ 1,000 |  |  |  |  |

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