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Marketable and Other Securities Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Marketable Securities [Line Items]
Cash and cash equivalents	$ 15,087		$ 15,087		$ 15,512
Sale proceeds from investments classified as available-for-sale and sold prior to maturity	1,000	$ 750	2,000	$ 1,400
GM Cruise [Member]
Marketable Securities [Line Items]
Cash and cash equivalents	2,000		2,000
GM Korea [Member]
Marketable Securities [Line Items]
Cash and cash equivalents	361		361
Level 3 [Member]
Marketable Securities [Line Items]
Adjustment of equity security to fair value	884		884
Level 3 [Member] | Interest Income and Other Non-Operating Income, Net [Member]
Marketable Securities [Line Items]
Unrealized gain on equity securities	$ 142		$ 142

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- Definition

Equity Securities, FV-NI

+ References

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- Definition

Equity Securities, FV-NI, Unrealized Gain

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- Definition

The total amount of proceeds received for the sale of securities, categorized neither as held-to-maturity nor trading securities, during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27357-111563

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- Definition

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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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