Discontinued Operations - Financial Information for Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Loss) income from discontinued operations, net of tax	$ (208)	$ 46	$ (185)	$ 72
Discontinued Operations, Held-for-sale [Member] | General Motors Holdings LLC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenue	143	154	274	298
Interest expense	23	41	46	82
Other expenses	79	60	156	131
Total costs and expenses	102	101	202	213
Income from discontinued operations before income taxes	41	53	72	85
Loss on sale of discontinued operations before income taxes	336	0	336	0
(Loss) income from discontinued operations before income taxes	(295)	53	(264)	85
Income tax (benefit) provision	(87)	7	(79)	13
(Loss) income from discontinued operations, net of tax	$ (208)	$ 46	$ (185)	$ 72