Fair Value Measurements - Input Hierarchy of Items Measured at Fair Value on a Recurring Basis (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Valuation Methodologies
Number of Days At Which Fair Value of Finance Receivables Is Measured	greater than 120 days past due or deemed to be uncollectible
Number Of Months Used To Determine Short Term Highly Liquid Investments Treatment As Cash Equivalents	3 months
Number Of Months Used To Determine Investments Treatment As Marketable Securities, Minimum	3 months
Term At Which Fair Value of Finance Receivables is Measured	120 days
Securities Purchased under Agreements to Resell [Abstract]
Securities Purchased under Agreements to Resell, Gross	$ 15,000,000	$ 228,000,000
Cash and cash equivalents
Valuation Methodologies
Number of months for evaluating classification of investments	three months or less from the date of acquisition
Marketable securities [Member]
Valuation Methodologies
Number of months for evaluating classification of investments	maturity date greater than three months at the date of purchase
Automotive [Member]
Derivative Financial Instrument Assets
Derivative financial instruments assets	517,000,000	580,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	713,000,000	418,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	206,000,000	233,000,000
Marketable securities
Marketable securities	17,135,000,000	20,157,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	517,000,000	580,000,000
Total assets at fair value	17,858,000,000	20,970,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	713,000,000	418,000,000
Total liabilities at fair value	713,000,000	418,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	64,000,000	33,000,000
Marketable securities
Marketable securities	6,758,000,000	10,348,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	122,000,000	200,000,000
Marketable securities
Marketable securities	7,004,000,000	6,538,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	20,000,000	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	2,738,000,000	2,623,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Equities [Member]
Marketable securities
Marketable securities	322,000,000	341,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	313,000,000	307,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Cash equivalents - financial instruments [Member]
Input Hierarchy of Items Measured at Fair Value on a Recurring Basis - Footnote Narrative
Par Value Assets Excluded From Fair Value By Input	3,300,000,000	2,800,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Cash [Member]
Input Hierarchy of Items Measured at Fair Value on a Recurring Basis - Footnote Narrative
Par Value Assets Excluded From Fair Value By Input	1,100,000,000	2,000,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	1,291,000,000	4,093,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	0	0
Total assets at fair value	1,291,000,000	4,093,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	0	0
Total liabilities at fair value	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | US Treasury and Government [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	969,000,000	3,752,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Equities [Member]
Marketable securities
Marketable securities	322,000,000	341,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	206,000,000	233,000,000
Marketable securities
Marketable securities	15,844,000,000	16,064,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	517,000,000	579,000,000
Total assets at fair value	16,567,000,000	16,876,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	710,000,000	416,000,000
Total liabilities at fair value	710,000,000	416,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | US Treasury and Government [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	64,000,000	33,000,000
Marketable securities
Marketable securities	5,789,000,000	6,596,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	122,000,000	200,000,000
Marketable securities
Marketable securities	7,004,000,000	6,538,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	20,000,000	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	2,738,000,000	2,623,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Equities [Member]
Marketable securities
Marketable securities	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	313,000,000	307,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	0	0
Derivative Financial Instrument Assets
Derivative financial instruments assets	0	1,000,000
Total assets at fair value	0	1,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	3,000,000	2,000,000
Total liabilities at fair value	3,000,000	2,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | US Treasury and Government [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Equities [Member]
Marketable securities
Marketable securities	0	0
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	0	0
Financial Services [Member]
Derivative Financial Instrument Assets
Derivative financial instruments assets	859,000,000	585,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	167,000,000	506,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	351,000,000	24,000,000
Marketable securities
Marketable securities	3,258,000,000	1,943,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	859,000,000	585,000,000
Total assets at fair value	4,468,000,000	2,552,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	167,000,000	506,000,000
Total liabilities at fair value	167,000,000	506,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Marketable securities
Marketable securities	1,268,000,000	443,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	341,000,000	24,000,000
Marketable securities
Marketable securities	405,000,000	184,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	10,000,000	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	1,555,000,000	1,273,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	30,000,000	43,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Cash equivalents - financial instruments [Member]
Input Hierarchy of Items Measured at Fair Value on a Recurring Basis - Footnote Narrative
Par Value Assets Excluded From Fair Value By Input	3,800,000,000	6,700,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Cash [Member]
Input Hierarchy of Items Measured at Fair Value on a Recurring Basis - Footnote Narrative
Par Value Assets Excluded From Fair Value By Input	2,000,000,000	2,800,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	17,000,000	418,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	0	0
Total assets at fair value	17,000,000	418,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	0	0
Total liabilities at fair value	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | US Treasury and Government [Member]
Marketable securities
Marketable securities	17,000,000	418,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	351,000,000	24,000,000
Marketable securities
Marketable securities	3,241,000,000	1,525,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	859,000,000	585,000,000
Total assets at fair value	4,451,000,000	2,134,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	167,000,000	506,000,000
Total liabilities at fair value	167,000,000	506,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | US Treasury and Government [Member]
Marketable securities
Marketable securities	1,251,000,000	25,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	341,000,000	24,000,000
Marketable securities
Marketable securities	405,000,000	184,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	10,000,000	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	1,555,000,000	1,273,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	30,000,000	43,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	0	0
Derivative Financial Instrument Assets
Derivative financial instruments assets	0	0
Total assets at fair value	0	0
Derivative financial instruments liabilities
Derivative financial instruments liabilities	0	0
Total liabilities at fair value	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | US Treasury and Government [Member]
Marketable securities
Marketable securities	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	0	0
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	$ 0	$ 0