Segment Information (Revenue by Product Group) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Information on revenue, net of intersegment eliminations, by product group
Revenue	$ 98,794	$ 97,114
Local voice and other retail services
Information on revenue, net of intersegment eliminations, by product group
Revenue	81,975	80,184
Wholesale carrier data services
Information on revenue, net of intersegment eliminations, by product group
Revenue	13,762	14,333
Data center colocation
Information on revenue, net of intersegment eliminations, by product group
Revenue	$ 3,057	$ 2,597