Segment Information - Total Assets (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Assets
Total assets:	$ 10,723	$ 9,699	$ 9,818
Reportable Segment Totals
Assets
Total assets:	10,381	9,451	9,615
Americas
Assets
Total assets:	5,994	5,497	5,402
Europe
Assets
Total assets:	3,342	3,036	3,232
Asia Pacific
Assets
Total assets:	1,045	918	981
Other
Assets
Total assets:	$ 342	$ 248	$ 203