Segment Information - Schedule of Segment Reporting Information to Consolidated Assets (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Assets	$ 18,219	$ 18,718
Cash and cash equivalents	1,205	2,150
Corporate fixed assets, net	5,628	5,594
Operating Segments
Segment Reporting Information [Line Items]
Assets	15,862	15,321
Segment Reconciling Items
Segment Reporting Information [Line Items]
Cash and cash equivalents	1,205	2,150
Deferred income taxes	675	743
Corporate fixed assets, net	307	310
Fair value of derivative contracts	53	91
Other	$ 117	$ 103