INAP JAPAN JOINT VENTURE - Unaudited Pro-Forma Financial Information (Details) - Internap Japan - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Revenue	$ 286,570,000	$ 305,733,000
Net loss attributable to INAP stockholders	$ (45,240,000)	$ (124,722,000)
Basic and diluted net loss per share (in dollars per share)	$ (2.38)	$ (9.53)