Acquisitions (Identifiable Intangible Assets Acquired) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	May. 18, 2015	Jan. 08, 2015
Sanbolic, Inc. [Member]
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired			$ 45,300
Intangible assets acquired	$ 45,300
Sanbolic, Inc. [Member] | Core and product technologies
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	43,800
Sanbolic, Inc. [Member] | Customer relationships
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 1,500
Finite-lived intangible assets acquired, Asset Life	2 years
Sanbolic, Inc. [Member] | Telecommunication carrier relationships
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 0
Sanbolic, Inc. [Member] | Trade names
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	0
Grasshopper Group, LLC [Member]
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired		$ 71,400
Intangible assets acquired	71,400
Grasshopper Group, LLC [Member] | Core and product technologies
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 25,000
Finite-lived intangible assets acquired, Asset Life	7 years
Grasshopper Group, LLC [Member] | Customer relationships
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 37,900
Finite-lived intangible assets acquired, Asset Life	5 years
Grasshopper Group, LLC [Member] | Telecommunication carrier relationships
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 7,900
Finite-lived intangible assets acquired, Asset Life	2 years
Grasshopper Group, LLC [Member] | Trade names
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 600
Finite-lived intangible assets acquired, Asset Life	2 years
Other 2015 Acquisition [Member]
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 980
Finite-lived intangible assets acquired, Asset Life	5 years
Intangible assets acquired	$ 980
Other 2015 Acquisition [Member] | Core and product technologies
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 980
Finite-lived intangible assets acquired, Asset Life	5 years
Other 2015 Acquisition [Member] | Customer relationships
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 0
Other 2015 Acquisition [Member] | Telecommunication carrier relationships
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	0
Other 2015 Acquisition [Member] | Trade names
Business Acquisition [Line Items]
Finite-lived Intangible assets acquired	$ 0
Minimum | Sanbolic, Inc. [Member] | Core and product technologies
Business Acquisition [Line Items]
Finite-lived intangible assets acquired, Asset Life	5 years
Maximum | Sanbolic, Inc. [Member] | Core and product technologies
Business Acquisition [Line Items]
Finite-lived intangible assets acquired, Asset Life	6 years