Debt and Commitments - Public Unsecured Debt Securities (Details) (Automotive [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Public Unsecured Debt Securities [Member]
Debt, principal amount	$ 6,795	$ 6,799
Debentures due March 26, 2015 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	161	165
Debt Instrument, Interest Rate, Stated Percentage	4.875%
Debentures due August 1, 2018 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	361	361
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Debentures due January 15, 2022 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	86	86
Debt Instrument, Interest Rate, Stated Percentage	8.875%
Debentures due November 15, 2025 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	209	209
Debt Instrument, Interest Rate, Stated Percentage	7.125%
Debentures due August 1, 2026 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	193	193
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Debentures due February 15, 2028 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	104	104
Debt Instrument, Interest Rate, Stated Percentage	6.625%
Debentures due October 1, 2028 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	638	638
Debt Instrument, Interest Rate, Stated Percentage	6.625%
Debentures due February 1, 2029 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	260	260
Debt Instrument, Interest Rate, Stated Percentage	6.375%
GLOBLS due July 16 2031 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	1,794	1,794
Debt Instrument, Interest Rate, Stated Percentage	7.45%
Debentures due January 15, 2032 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	151	151
Debt Instrument, Interest Rate, Stated Percentage	8.90%
Debentures due February 15, 2032 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	4	4
Debt Instrument, Interest Rate, Stated Percentage	9.95%
Debentures due April 2, 2035 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	40	40
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Debentures due June 15, 2043 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	73	73
Debt Instrument, Interest Rate, Stated Percentage	7.75%
Debentures due November 1, 2046 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	398	398
Debt Instrument, Interest Rate, Stated Percentage	7.40%
Debentures due February 15, 2047 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	181	181
Debt Instrument, Interest Rate, Stated Percentage	9.98%
Debentures due May 15, 2097 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	142	142
Debt Instrument, Interest Rate, Stated Percentage	7.70%
Notes Due January 15, 2043 [Member] | Public Unsecured Debt Securities [Member]
Debt, principal amount	2,000	2,000
Debt Instrument, Interest Rate, Stated Percentage	4.75%
Debentures due September 15, 2021 [Member]
Public Unsecured Debt Aggregate Principal Amount Outstanding of On Lent Securities	$ 180
Debentures due September 15, 2021 [Member] | Public Unsecured Debt Securities [Member]
Debt Instrument, Interest Rate, Stated Percentage	9.215%