Fair Value Measurements - Input Hierarchy of Items Measured at Fair Value on a Recurring Basis (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Automotive [Member]
Derivative Financial Instrument Assets
Derivative financial instruments assets	$ 1,102,000,000	$ 517,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	1,266,000,000	713,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	241,000,000	206,000,000
Marketable securities
Marketable securities	14,468,000,000	17,135,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	1,102,000,000	517,000,000
Total assets at fair value	15,811,000,000	17,858,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	1,266,000,000	713,000,000
Total liabilities at fair value	1,266,000,000	713,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	11,000,000	64,000,000
Marketable securities
Marketable securities	4,043,000,000	6,758,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	220,000,000	122,000,000
Marketable securities
Marketable securities	6,911,000,000	7,004,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	10,000,000	20,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	2,922,000,000	2,738,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Equities [Member]
Marketable securities
Marketable securities	270,000,000	322,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	322,000,000	313,000,000
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	3,500,000,000	3,300,000,000
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	1,400,000,000	1,100,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	0	0
Marketable securities
Marketable securities	1,023,000,000	1,291,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	0	0
Total assets at fair value	1,023,000,000	1,291,000,000
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	753,000,000	969,000,000
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	270,000,000	322,000,000
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	241,000,000	206,000,000
Marketable securities
Marketable securities	13,445,000,000	15,844,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	1,102,000,000	517,000,000
Total assets at fair value	14,788,000,000	16,567,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	1,260,000,000	710,000,000
Total liabilities at fair value	1,260,000,000	710,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | US Treasury and Government [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	11,000,000	64,000,000
Marketable securities
Marketable securities	3,290,000,000	5,789,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	220,000,000	122,000,000
Marketable securities
Marketable securities	6,911,000,000	7,004,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	10,000,000	20,000,000
Automotive [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	2,922,000,000	2,738,000,000
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	322,000,000	313,000,000
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	0
Total assets at fair value	0	0
Derivative financial instruments liabilities
Derivative financial instruments liabilities	6,000,000	3,000,000
Total liabilities at fair value	6,000,000	3,000,000
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	1,204,000,000	859,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	297,000,000	167,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	400,000,000	351,000,000
Marketable securities
Marketable securities	6,264,000,000	3,258,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	1,204,000,000	859,000,000
Total assets at fair value	7,868,000,000	4,468,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	297,000,000	167,000,000
Total liabilities at fair value	297,000,000	167,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Marketable securities
Marketable securities	4,006,000,000	1,268,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	320,000,000	341,000,000
Marketable securities
Marketable securities	521,000,000	405,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	80,000,000	10,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	1,706,000,000	1,555,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	31,000,000	30,000,000
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	5,100,000,000	3,800,000,000
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	1,800,000,000	2,000,000,000
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	1,151,000,000	17,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	0	0
Total assets at fair value	1,151,000,000	17,000,000
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	1,151,000,000	17,000,000
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	400,000,000	351,000,000
Marketable securities
Marketable securities	5,113,000,000	3,241,000,000
Derivative Financial Instrument Assets
Derivative financial instruments assets	1,204,000,000	859,000,000
Total assets at fair value	6,717,000,000	4,451,000,000
Derivative financial instruments liabilities
Derivative financial instruments liabilities	297,000,000	167,000,000
Total liabilities at fair value	297,000,000	167,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | US Treasury and Government [Member]
Marketable securities
Marketable securities	2,855,000,000	1,251,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign Government and Agencies [Member]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	320,000,000	341,000,000
Marketable securities
Marketable securities	521,000,000	405,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Domain]
Cash equivalents - financial instruments
Cash equivalents - financial instruments	80,000,000	10,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Member]
Marketable securities
Marketable securities	1,706,000,000	1,555,000,000
Financial Services [Member] | Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other marketable securities [Member]
Marketable securities
Marketable securities	31,000,000	30,000,000
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