Marketable and Other Securities - Fair Value of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Marketable Securities [Line Items]
Total cash and cash equivalents	$ 20,844	$ 15,512
Total restricted cash	2,652	2,336
Due in one year or less	11,288
Due between one and five years	4,406
Total available-for-sale debt securities with contractual maturities	15,694
GM Korea [Member]
Marketable Securities [Line Items]
Cash and time deposits	616
GM Cruise Segment [Member]
Marketable Securities [Line Items]
Total cash and cash equivalents	2,300
Cash And Cash Equivalents [Member]
Marketable Securities [Line Items]
Cash and time deposits	7,254	6,962
Total available-for-sale debt securities with contractual maturities	10,423	5,736
Cash And Cash Equivalents [Member] \| Level 2 [Member] \| U.S. government and agencies [Member]
Marketable Securities [Line Items]
Total available-for-sale debt securities with contractual maturities	4,656	750
Cash And Cash Equivalents [Member] \| Level 2 [Member] \| Corporate Debt [Member]
Marketable Securities [Line Items]
Total available-for-sale debt securities with contractual maturities	3,791	3,032
Cash And Cash Equivalents [Member] \| Level 2 [Member] \| Sovereign Debt [Member]
Marketable Securities [Line Items]
Total available-for-sale debt securities with contractual maturities	1,976	1,954
Cash And Cash Equivalents [Member] \| Level 1 [Member]
Marketable Securities [Line Items]
Money market funds	3,167	2,814
Marketable Securities [Member]
Marketable Securities [Line Items]
Total available-for-sale debt securities with contractual maturities	5,966	8,313
Marketable Securities [Member] \| Level 2 [Member] \| U.S. government and agencies [Member]
Marketable Securities [Line Items]
Total available-for-sale debt securities with contractual maturities	1,230	3,310
Marketable Securities [Member] \| Level 2 [Member] \| Corporate Debt [Member]
Marketable Securities [Line Items]
Total available-for-sale debt securities with contractual maturities	3,478	3,665
Marketable Securities [Member] \| Level 2 [Member] \| Sovereign Debt [Member]
Marketable Securities [Line Items]
Total available-for-sale debt securities with contractual maturities	563	703
Marketable Securities [Member] \| Level 2 [Member] \| Mortgage and asset-backed [Member]
Marketable Securities [Line Items]
Total available-for-sale debt securities with contractual maturities	695	635
Restricted cash - cash equivalents [Member]
Marketable Securities [Line Items]
Cash and cash equivalents	260	219
Restricted cash - cash equivalents [Member] \| Level 1 [Member]
Marketable Securities [Line Items]
Money market funds	$ 2,392	$ 2,117

Sum of cash (other than available-for-sale and trading securities) and time deposits.

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