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Marketable and Other Securities Narrative (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Marketable Securities [Line Items]
Cash and cash equivalents	$ 18,435			$ 18,435		$ 15,512
Sale proceeds from investments classified as available-for-sale and sold prior to maturity	1,700		$ 3,700	3,600	$ 5,100
GM Korea [Member]
Marketable Securities [Line Items]
Cash and cash equivalents	364			364
Level 3 [Member]
Marketable Securities [Line Items]
Fair value of equity securities	$ 884	$ 884		$ 884
Level 3 [Member] | Interest Income and Other Non-Operating Income, Net [Member]
Marketable Securities [Line Items]
Unrealized gain on equity securities		$ 142

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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