Business Segments - Segment Reporting Information, by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total assets	$ 18,044	$ 16,439	$ 17,437
Increase in corporate assets	2,080
Operating Segments
Segment Reporting Information [Line Items]
Total assets	14,570	13,219	15,506
Operating Segments | North America
Segment Reporting Information [Line Items]
Total assets	4,929	4,808	4,977
Operating Segments | Europe, Middle East and Africa
Segment Reporting Information [Line Items]
Total assets	4,957	4,383	5,532
Operating Segments | Asia Pacific
Segment Reporting Information [Line Items]
Total assets	2,594	2,559	2,613
Operating Segments | Latin America
Segment Reporting Information [Line Items]
Total assets	2,090	1,469	2,384
Corporate
Segment Reporting Information [Line Items]
Total assets	$ 3,474	$ 3,220	$ 1,931