SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Reclassifications (Details) - USD ($)	3 Months Ended								6 Months Ended	9 Months Ended	12 Months Ended			50 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018
Revenues:
Revenues	$ 78,238,000	$ 82,972,000	$ 81,962,000	$ 74,201,000	$ 70,035,000	$ 68,907,000	$ 69,642,000	$ 72,133,000			$ 317,373,000	$ 280,718,000	$ 298,297,000	$ 8,855
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization	$ 23,662,000	29,511,000	28,621,000	25,467,000	$ 25,798,000	$ 24,945,000	$ 26,429,000	$ 29,045,000	$ 54,088,000	$ 83,601,000	107,262,000	106,217,000	124,255,000
INAP COLO
Revenues:
Revenues												0	0
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												0	0
INAP CLOUD
Revenues:
Revenues												0	0
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												0	0
INAP US
Revenues:
Revenues											248,184,000	215,770,000	229,902,000
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												82,977,000	98,512,000
INAP INTL
Revenues:
Revenues											$ 69,189,000	64,948,000	68,395,000
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												23,220,000	25,743,000
As Previously Reported
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization		$ 28,866,000	$ 27,976,000	$ 25,037,000					$ 53,013,000	$ 81,880,000
As Previously Reported | INAP COLO
Revenues:
Revenues												209,580,000	221,678,000
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												89,240,000	105,620,000
As Previously Reported | INAP CLOUD
Revenues:
Revenues												71,138,000	76,619,000
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												16,977,000	18,635,000
As Previously Reported | INAP US
Revenues:
Revenues												0	0
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												0	0
As Previously Reported | INAP INTL
Revenues:
Revenues												0	0
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												0	0
Reclassification | INAP COLO
Revenues:
Revenues												(209,580,000)	(221,678,000)
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												(89,240,000)	(105,620,000)
Reclassification | INAP CLOUD
Revenues:
Revenues												(71,138,000)	(76,619,000)
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												(16,977,000)	(18,635,000)
Reclassification | INAP US
Revenues:
Revenues												215,770,000	229,902,000
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												82,997,000	98,512,000
Reclassification | INAP INTL
Revenues:
Revenues												64,948,000	68,395,000
Costs of sales and services, exclusive of depreciation and amortization, shown below:
Costs of sales and services, exclusive of depreciation and amortization												$ 23,220,000	$ 25,743,000