Cash, Cash Equivalents, and Marketable Securities Available for Sale Securities (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 1,327,000,000	$ 491,000,000	$ 4,173,000,000	$ 3,107,000,000
Available-for-sale Securities, Gross Realized Gains	0	0	1,000,000	3,000,000
Available-for-sale Securities, Gross Realized Losses	4,000,000	$ 0	15,000,000	8,000,000
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities			0	$ 0
Operating Segments [Member] | Automotive
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	11,919,000,000		11,919,000,000		$ 11,338,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,000,000		1,000,000		1,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(147,000,000)		(147,000,000)		(69,000,000)
Available-for-sale Securities	11,773,000,000		11,773,000,000		11,270,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	2,784,000,000		2,784,000,000		2,033,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	8,893,000,000		8,893,000,000		9,190,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	96,000,000		96,000,000		47,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	5,786,000,000		5,786,000,000		8,551,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(71,000,000)		(71,000,000)		(49,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	5,082,000,000		5,082,000,000		1,673,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(76,000,000)		(76,000,000)		(20,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	10,868,000,000		10,868,000,000		10,224,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(147,000,000)		(147,000,000)		(69,000,000)
Operating Segments [Member] | Automotive | U.S. government
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,909,000,000		2,909,000,000		3,669,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0		0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(19,000,000)		(19,000,000)		(18,000,000)
Available-for-sale Securities	2,890,000,000		2,890,000,000		3,651,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	1,926,000,000		1,926,000,000		1,377,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	964,000,000		964,000,000		2,274,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	0		0		0
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	869,000,000		869,000,000		2,382,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3,000,000)		(3,000,000)		(9,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,869,000,000		1,869,000,000		903,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(16,000,000)		(16,000,000)		(9,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,738,000,000		2,738,000,000		3,285,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(19,000,000)		(19,000,000)		(18,000,000)
Operating Segments [Member] | Automotive | U.S. government agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,930,000,000		1,930,000,000		1,915,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0		0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(26,000,000)		(26,000,000)		(15,000,000)
Available-for-sale Securities	1,904,000,000		1,904,000,000		1,900,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	514,000,000		514,000,000		265,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	1,372,000,000		1,372,000,000		1,620,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	18,000,000		18,000,000		15,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	476,000,000		476,000,000		1,625,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(4,000,000)		(4,000,000)		(12,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,386,000,000		1,386,000,000		260,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(22,000,000)		(22,000,000)		(3,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,862,000,000		1,862,000,000		1,885,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(26,000,000)		(26,000,000)		(15,000,000)
Operating Segments [Member] | Automotive | Non-U.S. government and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	3,960,000,000		3,960,000,000		4,021,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0		0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(68,000,000)		(68,000,000)		(28,000,000)
Available-for-sale Securities	3,892,000,000		3,892,000,000		3,993,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	144,000,000		144,000,000		197,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	3,748,000,000		3,748,000,000		3,771,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	0		0		25,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	2,110,000,000		2,110,000,000		3,148,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(39,000,000)		(39,000,000)		(20,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,453,000,000		1,453,000,000		510,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(29,000,000)		(29,000,000)		(8,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,563,000,000		3,563,000,000		3,658,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(68,000,000)		(68,000,000)		(28,000,000)
Operating Segments [Member] | Automotive | Corporate debt
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,911,000,000		2,911,000,000		1,716,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,000,000		1,000,000		1,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(33,000,000)		(33,000,000)		(8,000,000)
Available-for-sale Securities	2,879,000,000		2,879,000,000		1,709,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	199,000,000		199,000,000		194,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	2,678,000,000		2,678,000,000		1,509,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	2,000,000		2,000,000		6,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	2,161,000,000		2,161,000,000		1,396,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(24,000,000)		(24,000,000)		(8,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	374,000,000		374,000,000		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(9,000,000)		(9,000,000)		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,535,000,000		2,535,000,000		1,396,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(33,000,000)		(33,000,000)		(8,000,000)
Operating Segments [Member] | Automotive | Other marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	209,000,000		209,000,000		17,000,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0		0		0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,000,000)		(1,000,000)		0
Available-for-sale Securities	208,000,000		208,000,000		17,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	1,000,000		1,000,000		0
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	131,000,000		131,000,000		16,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	76,000,000		76,000,000		$ 1,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	170,000,000		170,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,000,000)		(1,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	170,000,000		170,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (1,000,000)		$ (1,000,000)