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Stock Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Stock Incentive Awards Units Outstanding (Roll Forward)
Units outstanding at beginning of period (in shares)	52,900,000
Granted (in shares)	13,700,000		0
Settled (in shares)	(10,200,000)
Forfeited or expired (in shares)	(8,300,000)
Units outstanding at end of period (in shares)	48,100,000	52,900,000
Stock Incentive Awards Weighted Average Grant Date Fair Value (Per Share) [Roll Forward]
Weighted-average grant date fair value, Units outstanding at beginning of period (in dollars per share)	$ 21.75
Weighted-average grant date fair value, granted (in dollars per share)	30.41
Weighted-average grant date fair value, settled (in dollars per share)	30.23
Weighted-average grant date fair value, forfeited or expired (in dollars per share)	29.51
Weighted-average grant date fair value, Units outstanding at end of period (in dollars per share)	$ 21.75	$ 21.75		$ 19.81
Remaining Contractual Term [Abstract]
Weighted Average Remaining Contractual Terms in years, Outstanding	1 year 3 months 18 days	2 years
Compensation expense	$ 316	$ 585	$ 627
Unrecognized compensation expense				$ 208
Weighted-average period for total unrecognized compensation expense for nonvested equity awards	1 year 3 months 18 days
Fair value of stock incentive awards vested	$ 317	$ 421	$ 325
Restricted Stock Units (RSUs) [Member]
Stock Incentive Plans Narratives [Abstract]
Service period	3 years
Performance Share Units (PSUs) [Member]
Stock Incentive Plans Narratives [Abstract]
Performance period	3 years
Stock options [Member]
Stock Incentive Plans Narratives [Abstract]
Expiration period	10 years
Remaining Contractual Term [Abstract]
Dividend yield	3.69%	4.43%
Expected volatility	28.00%	25.00%
Risk-free interest rate	2.73%	1.97%
Expected option life	5 years 11 months 23 days	5 years 10 months 2 days
Performance-based Employee Stock Options [Member]
Stock Incentive Plans Narratives [Abstract]
Service period	55 months
Service-based Employee Stock Options [Member] | Minimum [Member]
Stock Incentive Plans Narratives [Abstract]
Service period	19 months
Service-based Employee Stock Options [Member] | Maximum [Member]
Stock Incentive Plans Narratives [Abstract]
Service period	3 years
Restricted Stock Awards (RSAs) [Member]
Stock Incentive Plans Narratives [Abstract]
Service period	3 years
GM Cruise Stock Incentive Awards [Member]
Stock Incentive Awards Units Outstanding (Roll Forward)
Granted (in shares)		0	0
GM Cruise Stock Incentive Awards [Member] | Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Stock Incentive Plans Narratives [Abstract]
Service period	4 years
GM Cruise Stock Incentive Awards [Member] | Stock options [Member]
Stock Incentive Plans Narratives [Abstract]
Expiration period	10 years
Remaining Contractual Term [Abstract]
Unrecognized compensation expense				$ 392
Weighted-average period for total unrecognized compensation expense for nonvested equity awards	8 years 6 months
GM Cruise Stock Incentive Awards [Member] | Stock options [Member] | Minimum [Member]
Stock Incentive Plans Narratives [Abstract]
Service period	4 years
GM Cruise Stock Incentive Awards [Member] | Stock options [Member] | Maximum [Member]
Stock Incentive Plans Narratives [Abstract]
Service period	10 years

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The weighted average grant date fair value of options and equity instruments other than options issued during the period, including both vested and nonvested instruments.

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Number of options and equity Instruments other than options outstanding, including both vested and non-vested instruments.

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Number of option and non-option equity instruments exercised by participants.

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Number of shares under option and non-option equity instrument agreements that were either cancelled or expired.

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Net number of option and non-option equity instruments granted to participants.

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The weighted average fair value of nonvested awards on equity-based plans including option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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Weighted average fair value as of the grant date of stock options and non-option equity instruments that were not exercised or put into effect as a result of the occurrence of a terminating event.

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Weighted average remaining contractual term for option and non-option equity-based awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The total fair value of options and non-option equity instruments that vested during the period.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Weighted average expected volatility rate of share-based compensation awards.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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