Consolidated Statements of Shareholder's Equity Statement (USD $) In Millions, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Balance at beginning of period at Dec. 31, 2011		$ 0	$ 3,470	$ (7)	$ 460
Balance at beginning of period (shares) at Dec. 31, 2011		500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)		0
Common stock issued		0
Share-based compensation expense			4
Capital contribution from GM			0
Salary stock plan modification			(15)
Differences between tax payments due under consolidated return and separate return basis			0
Other comprehensive (loss) income, net of income tax				4
Net income	463				463
Balance at end of period at Dec. 31, 2012		0	3,459	(3)	923
Balance at end of period (shares) at Dec. 31, 2012		500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)		2
Common stock issued		0
Share-based compensation expense			10
Capital contribution from GM			1,300
Salary stock plan modification			0
Differences between tax payments due under consolidated return and separate return basis			16
Other comprehensive (loss) income, net of income tax				14
Net income	566				566
Balance at end of period at Dec. 31, 2013	6,285	0	4,785	11	1,489
Balance at end of period (shares) at Dec. 31, 2013		502
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)		3
Common stock issued		0
Share-based compensation expense			18
Capital contribution from GM			996
Salary stock plan modification			0
Differences between tax payments due under consolidated return and separate return basis			0
Other comprehensive (loss) income, net of income tax				(444)
Net income	537				537
Balance at end of period at Dec. 31, 2014	$ 7,392	$ 0	$ 5,799	$ (433)	$ 2,026
Balance at end of period (shares) at Dec. 31, 2014		505