SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended	9 Months Ended	12 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	Jan. 01, 2018	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Costs of sales and services, exclusive of depreciation and amortization	$ 23,662	$ 29,511	$ 28,621	$ 25,467	$ 25,798	$ 24,945	$ 26,429	$ 29,045	$ 54,088	$ 83,601	$ 107,262	$ 106,217	$ 124,255
Depreciation and amortization		23,309	22,468	20,996					43,464	66,771	90,676	74,993	76,948
Interest expense		16,003	14,981	14,450					29,431	45,435	68,132	50,476	30,909
Net loss attributable to INAP shareholders	(18,454)	(15,479)	(14,279)	(14,288)	(6,934)	$ (10,895)	$ (19,283)	$ (8,230)	(28,567)	(44,046)	(62,500)	(45,343)	(124,742)
Property and equipment, net	478,061	487,616	463,273	471,752	458,565				463,273	487,616	478,061	458,565
Total assets	744,931	756,231	735,022	742,358	586,525				735,022	756,231	744,931	586,525
Capital lease obligations	9,080	263,544	231,415	234,019	11,711				231,415	263,544	9,080	11,711
Total liabilities	744,874	775,949	740,422	733,568	587,557				740,422	775,949	744,874	587,557
Accumulated deficit	(1,363,019)	(1,344,566)	(1,329,086)	(1,313,826)	(1,323,723)				(1,329,086)	(1,344,566)	(1,363,019)	(1,323,723)		$ (1,300,519)
Total stockholders' equity (deficit)	$ 57	(19,923)	(5,605)	8,594	$ (1,032)				(5,605)	(19,923)	$ 57	$ (1,032)	$ (3,724)		$ 114,436
As reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Costs of sales and services, exclusive of depreciation and amortization		28,866	27,976	25,037					53,013	81,880
Depreciation and amortization		23,431	22,590	21,077					43,667	67,097
Interest expense		16,898	15,860	15,027					30,887	47,786
Net loss attributable to INAP shareholders		(15,106)	(13,923)	(14,060)					(27,983)	(43,089)
Property and equipment, net		477,423	452,958	461,314					452,958	477,423
Total assets		746,038	724,707	731,920					724,707	746,038
Capital lease obligations		252,599	220,721	223,549					220,721	252,599
Total liabilities		765,004	729,728	723,098					729,728	765,004
Accumulated deficit		(1,343,609)	(1,328,502)	(1,313,598)					(1,328,502)	(1,343,609)
Total stockholders' equity (deficit)		(18,966)	(5,021)	8,822					(5,021)	(18,966)
Adjustments | Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Costs of sales and services, exclusive of depreciation and amortization		645	645	430					1,075	1,721
Depreciation and amortization		(122)	(122)	(81)					(203)	(326)
Interest expense		(895)	(879)	(577)					(1,456)	(2,351)
Net loss attributable to INAP shareholders		(373)	(356)	(228)					(584)	(957)
Property and equipment, net		10,193	10,315	10,438					10,315	10,193
Total assets		10,193	10,315	10,438					10,315	10,193
Capital lease obligations		10,945	10,694	10,470					10,694	10,945
Total liabilities		10,945	10,694	10,470					10,694	10,945
Accumulated deficit		(957)	(584)	(228)					(584)	(957)
Total stockholders' equity (deficit)		$ (957)	$ (584)	$ (228)					$ (584)	$ (957)