Debt and Commitments - Public Unsecured Debt Securities (Details) - Operating Segments [Member] - Automotive - Corporate debt - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Debt, principal amount	$ 9,394	$ 6,594
Debentures due August 1, 2018 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 361	361
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Debentures due January 15, 2022 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 86	86
Debt Instrument, Interest Rate, Stated Percentage	8.875%
Debentures due November 15, 2025 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 209	209
Debt Instrument, Interest Rate, Stated Percentage	7.125%
Debentures due August 1, 2026 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 193	193
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Debentures due February 15, 2028 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 104	104
Debt Instrument, Interest Rate, Stated Percentage	6.625%
Debentures due October 1, 2028 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 638	638
Debt Instrument, Interest Rate, Stated Percentage	6.625%
Debentures due February 1, 2029 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 260	260
Debt Instrument, Interest Rate, Stated Percentage	6.375%
GLOBLS due July 16 2031 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 1,794	1,794
Debt Instrument, Interest Rate, Stated Percentage	7.45%
Debentures due January 15, 2032 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 151	151
Debt Instrument, Interest Rate, Stated Percentage	8.90%
Debentures due February 15, 2032 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 4	4
Debt Instrument, Interest Rate, Stated Percentage	9.95%
Debentures due June 15, 2043 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 73	73
Debt Instrument, Interest Rate, Stated Percentage	7.75%
Debentures due November 1, 2046 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 398	398
Debt Instrument, Interest Rate, Stated Percentage	7.40%
Debentures due February 15, 2047 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 181	181
Debt Instrument, Interest Rate, Stated Percentage	9.98%
Debentures due May 15, 2097 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 142	142
Debt Instrument, Interest Rate, Stated Percentage	7.70%
Notes Due December 8, 2026 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 1,500	0
Debt Instrument, Interest Rate, Stated Percentage	4.346%
Notes Due December 8, 2046 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 1,300	0
Debt Instrument, Interest Rate, Stated Percentage	5.291%
Notes Due January 15, 2043 [Member]
Debt Instrument [Line Items]
Debt, principal amount	$ 2,000	$ 2,000
Debt Instrument, Interest Rate, Stated Percentage	4.75%
Debentures due September 15, 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	9.215%
Public Unsecured Debt Aggregate Principal Amount Outstanding of On Lent Securities	$ 180