Summary of Significant Accounting Policies - Property & Equipment (Details)	12 Months Ended
	Dec. 31, 2016
Network equipment | Minimum
Property, Plant and Equipment
Useful life of property and equipment	3 years
Network equipment | Maximum
Property, Plant and Equipment
Useful life of property and equipment	25 years
Buildings | Minimum
Property, Plant and Equipment
Useful life of property and equipment	3 years
Buildings | Maximum
Property, Plant and Equipment
Useful life of property and equipment	30 years
Computer software, office equipment and other | Minimum
Property, Plant and Equipment
Useful life of property and equipment	2 years
Computer software, office equipment and other | Maximum
Property, Plant and Equipment
Useful life of property and equipment	5 years