Deferred Subscription Solicitation and Commission Costs - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred subscription solicitation and commission costs	$ 1,655	$ 5,050
Amortization of deferred subscription solicitation costs, net of write-offs	10,300	12,600
Marketing costs	$ 1,800	$ 1,500

Deferred subscription solicitation costs consist of subscription acquisition costs, including telemarketing, web-based marketing expenses and direct mail such as printing and postage.

No definition available.

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Namespace Prefix:	intx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant