CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Network operations, equity-based compensation expense	$ 573	$ 584	$ 488
Selling, general, and administrative, equity-based compensation expense	$ 10,162	$ 10,931	$ 9,083

This element represents the expenses related to equity based compensation, which includes selling, general and administrative expenses, during the reporting period by the entity.

No definition available.

Name:	ccoi_SellingGeneralAndAdministrativeExpensesIncludeEquityBasedCompensationExpense
Namespace Prefix:	ccoi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration