CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Network operations, equity-based compensation expense	$ 172	$ 113
Selling, general, and administrative, equity-based compensation expense	$ 2,969	$ 1,893

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