Discontinued Operations - Financial Information for Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Loss) income from discontinued operations, net of tax	$ (255)	$ 16	$ (208)	$ 23	$ 0	$ (424)	$ 97
Discontinued Operations, Held-for-sale [Member] | European Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenue						474	574
Interest expense						79	136
Other expenses						263	287
Total costs and expenses						342	423
Income from discontinued operations before income taxes						132	151
Loss on sale of discontinued operations before income taxes						525	0
(Loss) income from discontinued operations before income taxes						(393)	151
Income tax provision						31	54
(Loss) income from discontinued operations, net of tax						$ (424)	$ 97