Goodwill and Intangible Assets - Goodwill Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in the carrying amount of goodwill
Balance of Goodwill at beginning of period		$ 2,590	$ 2,462	$ 2,489
Acquisition related adjustments				41
Translation effects		(77)	128	(68)
Balance of Goodwill at end of the period	$ 2,513	2,513	2,590	2,462
Impairment charge	0
Europe
Changes in the carrying amount of goodwill
Balance of Goodwill at beginning of period		913	808	840
Translation effects		(39)	105	(32)
Balance of Goodwill at end of the period	874	874	913	808
Americas
Changes in the carrying amount of goodwill
Balance of Goodwill at beginning of period		1,672	1,649	1,644
Acquisition related adjustments				41
Translation effects		(38)	23	(36)
Balance of Goodwill at end of the period	1,634	1,634	1,672	1,649
Other
Changes in the carrying amount of goodwill
Balance of Goodwill at beginning of period		5	5	5
Balance of Goodwill at end of the period	5	5	5	5
Asia Pacific
Changes in the carrying amount of goodwill
Balance of Goodwill at beginning of period		0	0	0
Balance of Goodwill at end of the period			0	0
Accumulated impairment losses	$ 1,135	$ 1,135	$ 1,135	$ 1,135