OPERATING SEGMENTS - Summary of operating results for business segments - (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Data center services									$ 167,286	$ 133,453	$ 128,200
IP services									106,306	111,175	115,964
Total revenues	69,748	68,129	68,687	67,028	62,800	62,014	60,410	59,404	273,592	244,628	244,164
Direct costs of network, sales and services, exclusive of depreciation and amortization:
Data center services									90,604	78,907	82,761
IP services									40,350	41,403	44,662
Total direct costs of network, sales and services, exclusive of depreciation and amortization	33,585	33,573	32,641	31,154	29,924	30,787	30,569	29,030	130,954	120,310	127,423
Segment profit:
Data center services									76,682	54,546	45,439
IP services									65,956	69,772	71,302
Total segment profit									142,638	124,318	116,741
Exit activities, restructuring and impairments	610	124	645	43	1,217	123	1,304	189	1,422	2,833	1,411
Other operating expenses, including direct costs of customer support, depreciation and amortization									137,452	125,408	116,226
Income (loss) from operations									3,764	(3,923)	(896)
Non-operating expense									7,849	3,866	2,170
Loss before income taxes and equity in (earnings) of equity-method investment									$ (4,085)	$ (7,789)	$ (3,066)