UNAUDITED QUARTERLY RESULTS - Summary of Unaudited Quarterly Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net revenues	$ 71,650	$ 72,960	$ 73,022	$ 73,873	$ 77,155	$ 82,928	$ 82,253	$ 73,822	$ 146,668	$ 156,075	$ 219,628	$ 239,003	$ 291,505	$ 316,158	$ 280,718
Costs of sales and services, exclusive of depreciation and amortization	27,703	27,549	26,045	25,649	27,022	28,212	27,638	24,777	$ 51,694	$ 52,415	$ 79,243	$ 80,628	106,946	107,649	106,217
Costs of customer support	6,450	8,145	8,726	8,790	8,305	7,984	8,841	7,387					32,111	32,517	25,757
Exit activities, restructuring and impairments	3,547	3,792	231	1,416	2,266	2,347	826	(33)					$ 8,986	$ 5,406	$ 6,249
Net loss attributable to INAP shareholders	$ (76,178)	$ (24,083)	$ (17,982)	$ (20,007)	$ (18,880)	$ (14,840)	$ (13,802)	$ (13,678)
Basic and diluted net loss per share (in dollars per share)	$ (3.21)	$ (1.02)	$ (0.76)	$ (0.85)	$ (0.80)	$ (0.73)	$ (0.69)	$ (0.68)					$ (5.81)	$ (2.95)	$ (2.33)