Segment information (Long-lived Assets by Geographic Information) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Long Lived Assets [Abstract]
Total long-lived assets	$ 4,989	$ 4,961
United States [Member]
Long Lived Assets [Abstract]
Total long-lived assets	2,349	2,328
Puerto Rico [Member]
Long Lived Assets [Abstract]
Total long-lived assets	1,527	1,591
ROW [Member]
Long Lived Assets [Abstract]
Total long-lived assets	$ 1,113	$ 1,042