Cash, Cash Equivalents, and Marketable Securities Available for Sale Securities (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$ 1,507,000,000	$ 1,315,000,000	$ 2,846,000,000	$ 2,616,000,000
Available-for-sale Securities, Gross Realized Gains	1,000,000	2,000,000	1,000,000	3,000,000
Available-for-sale Securities, Gross Realized Losses	5,000,000	$ 6,000,000	11,000,000	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	11,511,000,000		11,511,000,000		$ 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	(144,000,000)		(144,000,000)		(69,000,000)
Available-for-sale Securities	11,368,000,000		11,368,000,000		11,270,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	2,282,000,000		2,282,000,000		2,033,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	9,007,000,000		9,007,000,000		9,190,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	79,000,000		79,000,000		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	6,149,000,000		6,149,000,000		8,551,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(92,000,000)		(92,000,000)		(49,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,126,000,000		4,126,000,000		1,673,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(52,000,000)		(52,000,000)		(20,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	10,275,000,000		10,275,000,000		10,224,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(144,000,000)		(144,000,000)		(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	2,634,000,000		2,634,000,000		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	(21,000,000)		(21,000,000)		(18,000,000)
Available-for-sale Securities	2,613,000,000		2,613,000,000		3,651,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	1,777,000,000		1,777,000,000		1,377,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	836,000,000		836,000,000		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	544,000,000		544,000,000		2,382,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(5,000,000)		(5,000,000)		(9,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,968,000,000		1,968,000,000		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	2,512,000,000		2,512,000,000		3,285,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(21,000,000)		(21,000,000)		(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	1,871,000,000		1,871,000,000		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	1,845,000,000		1,845,000,000		1,900,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	309,000,000		309,000,000		265,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	1,518,000,000		1,518,000,000		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	966,000,000		966,000,000		1,625,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(14,000,000)		(14,000,000)		(12,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	848,000,000		848,000,000		260,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(12,000,000)		(12,000,000)		(3,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,814,000,000		1,814,000,000		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	4,178,000,000		4,178,000,000		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	(63,000,000)		(63,000,000)		(28,000,000)
Available-for-sale Securities	4,115,000,000		4,115,000,000		3,993,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	6,000,000		6,000,000		197,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	4,109,000,000		4,109,000,000		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	2,450,000,000		2,450,000,000		3,148,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(43,000,000)		(43,000,000)		(20,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,120,000,000		1,120,000,000		510,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(20,000,000)		(20,000,000)		(8,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,570,000,000		3,570,000,000		3,658,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(63,000,000)		(63,000,000)		(28,000,000)
Operating Segments [Member] | Automotive | Corporate debt
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,628,000,000		2,628,000,000		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	2,596,000,000		2,596,000,000		1,709,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	190,000,000		190,000,000		194,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	2,404,000,000		2,404,000,000		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	2,033,000,000		2,033,000,000		1,396,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(29,000,000)		(29,000,000)		(8,000,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	190,000,000		190,000,000		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(4,000,000)		(4,000,000)		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,223,000,000		2,223,000,000		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	200,000,000		200,000,000		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	199,000,000		199,000,000		17,000,000
Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value	0		0		0
Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value	140,000,000		140,000,000		16,000,000
Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value	59,000,000		59,000,000		$ 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	156,000,000		156,000,000
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	156,000,000		156,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (1,000,000)		$ (1,000,000)