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Equity In Net Assets Of Nonconsolidated Affiliates (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) joint_venture	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity income	$ 2,132	$ 2,282	$ 2,193
Equity Method Investments	9,073	8,996	9,195
Basis Difference	$ 4,300	4,300
Number of joint ventures engaged in production, import and sale of products | joint_venture	4
SGM [Member]
Schedule of Equity Method Investments [Line Items]
Number of interests in other joint ventures | joint_venture	3
Automotive China [Member]
Schedule of Equity Method Investments [Line Items]
Equity income	$ 1,976	1,973	2,057
Equity Method Investments	7,832	7,859
Other joint ventures [Member]
Schedule of Equity Method Investments [Line Items]
Equity income	156	309	$ 136
Equity Method Investments	$ 1,241	$ 1,137
SGM [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%	50.00%
SGM [Member] | SAIC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%
FAW-GM [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%	50.00%
PATAC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%	50.00%
SGMS [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	49.00%	49.00%
SGMW [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	44.00%	44.00%
Shanghai OnStar [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	40.00%	40.00%
Shanghai OnStar [Member] | SGM [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	20.00%
SGM Norsom [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	25.00%	25.00%
SGM Norsom [Member] | SGM [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
SGM Norsom [Member] | SAIC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		25.00%
SGM DY [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	25.00%	25.00%
SGM DY [Member] | SGM [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
SGM DY [Member] | SAIC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		25.00%
SGM DYPT [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	25.00%	25.00%
SGM DYPT [Member] | SGM [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		50.00%
SGM DYPT [Member] | SAIC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage		25.00%
Shanghai Chengxin [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	0.00%	33.00%
SAIC-GMAC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	35.00%	35.00%
SAIC-GMAC [Member] | SGM [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	20.00%
SAIC-GMAC [Member] | Shanghai Automotive Group Finance Company Ltd. [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	45.00%
SGM Norsom, SGM DY and SGM DYPT [Member] | SGM [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	50.00%
SGM Norsom, SGM DY and SGM DYPT [Member] | SAIC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage	25.00%

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