Segment Information (Identifiable Assets By Segment) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Identifiable assets	$ 5,481,438	$ 5,512,007
Long-lived assets	373,817	367,779
United States
Segment Reporting Information [Line Items]
Long-lived assets	294,982	284,463
United Kingdom
Segment Reporting Information [Line Items]
Long-lived assets	28,851	29,556
Other countries
Segment Reporting Information [Line Items]
Long-lived assets	49,984	53,760
Enterprise and Service Provider
Segment Reporting Information [Line Items]
Identifiable assets	4,578,436	4,879,513
Mobility Apps division
Segment Reporting Information [Line Items]
Identifiable assets	$ 903,002	$ 632,494