Business Segments - Capital Expenditures Depreciation and Amortization (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Capital expenditures	$ 881	$ 996	$ 983
Depreciation and amortization	781	727	698
Operating Segments
Segment Reporting Information [Line Items]
Capital expenditures	848	946	965
Depreciation and amortization	713	678	664
Operating Segments | Americas
Segment Reporting Information [Line Items]
Capital expenditures	525	618	618
Depreciation and amortization	398	366	364
Operating Segments | Europe, Middle East and Africa
Segment Reporting Information [Line Items]
Capital expenditures	159	191	223
Depreciation and amortization	191	192	186
Operating Segments | Asia Pacific
Segment Reporting Information [Line Items]
Capital expenditures	164	137	124
Depreciation and amortization	124	120	114
Corporate
Segment Reporting Information [Line Items]
Capital expenditures	33	50	18
Depreciation and amortization	$ 68	$ 49	$ 34