OPERATING SEGMENT AND GEOGRAPHIC INFORMATION - Summary of Operating Results for Business Segments (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Revenues	$ 70,035,000	$ 68,907,000	$ 69,642,000	$ 72,133,000	$ 74,117,000	$ 73,940,000	$ 74,315,000	$ 75,924,000	$ 280,718,000	$ 298,297,000	$ 318,293,000
Costs of sales and services, exclusive of depreciation and amortization:
Costs of sales and services, exclusive of depreciation and amortization	25,798,000	24,945,000	26,429,000	29,045,000	30,246,000	31,562,000	31,370,000	31,077,000	106,217,000	124,255,000	131,440,000
Segment profit:
Segment profit									174,501,000	174,042,000	186,853,000
Goodwill impairment					1,936,000	78,169,000	0	0	0	80,105,000	0
Exit activities, restructuring and impairments	$ (148,000)	$ 745,000	$ 4,628,000	$ 1,023,000	$ 5,213,000	$ 1,670,000	$ 152,000	$ 201,000	6,249,000	7,236,000	2,278,000
Other operating expenses, including direct costs of customer support, depreciation and amortization									163,478,000	179,770,000	210,470,000
Income (loss) from operations									4,774,000	(93,070,000)	(25,895,000)
Non-operating expenses									51,001,000	31,312,000	26,408,000
Loss from continuing operations before income taxes, non-controlling interest and equity in (earnings) of equity-method investment									(46,227,000)	(124,382,000)	(52,303,000)
INAP COLO
Revenues:
Revenues									209,580,000	221,678,000	234,859,000
Costs of sales and services, exclusive of depreciation and amortization:
Costs of sales and services, exclusive of depreciation and amortization									89,240,000	105,620,000	111,765,000
Segment profit:
Segment profit									120,340,000	116,058,000	123,094,000
INAP CLOUD
Revenues:
Revenues									71,138,000	76,619,000	83,434,000
Costs of sales and services, exclusive of depreciation and amortization:
Costs of sales and services, exclusive of depreciation and amortization									16,977,000	18,635,000	19,675,000
Segment profit:
Segment profit									$ 54,161,000	$ 57,984,000	$ 63,759,000