Segment Information (Identifiable Assets By Segment) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Identifiable assets	$ 5,512,007	$ 5,212,249
Long-lived assets	367,779	338,996
United States
Segment Reporting Information [Line Items]
Long-lived assets	284,463	258,114
United Kingdom
Segment Reporting Information [Line Items]
Long-lived assets	29,556	29,382
Other countries
Segment Reporting Information [Line Items]
Long-lived assets	53,760	51,500
Enterprise and Service Provider division
Segment Reporting Information [Line Items]
Identifiable assets	4,879,513	4,595,916
Mobility Apps division
Segment Reporting Information [Line Items]
Identifiable assets	$ 632,494	$ 616,333