NET LOSS PER SHARE - Schedule of basic and diluted net loss per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net loss	$ (14,033)	$ (8,230)
Less net income attributable to non-controlling interest	27	0
Net loss attributable to INAP stockholders	$ (14,060)	$ (8,230)
Weighted average shares outstanding, basic and diluted (in shares)	20,052	16,087
Net loss per share, basic and diluted (in dollars per share)	$ (0.70)	$ (0.50)
Anti-dilutive securities excluded from diluted net loss per share calculation for stock-based compensation plans (in shares)	1,336	1,385