Business Segments - Segment Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Assets	$ 16,872	$ 17,064
Operating Segments
Segment Reporting Information [Line Items]
Assets	14,571	14,599
Operating Segments | Americas
Segment Reporting Information [Line Items]
Assets	7,160	6,923
Operating Segments | Europe, Middle East and Africa
Segment Reporting Information [Line Items]
Assets	4,809	4,995
Operating Segments | Asia Pacific
Segment Reporting Information [Line Items]
Assets	2,602	2,681
Corporate
Segment Reporting Information [Line Items]
Assets	$ 2,301	$ 2,465