Represents the notice period required for cancellation of lease.

No definition available.

Name:	ccoi_LesseeLeasingArrangementsRequiredNoticePeriodForCancellationOfLease
Namespace Prefix:	ccoi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of owners of the partnership or LLC.

+ References

No definition available.

+ Details

Name:	ccoi_RelatedPartyTransactionNumberOfOwners
Namespace Prefix:	ccoi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of interest held by the related parties in the partnership.

+ References

No definition available.

+ Details

Name:	ccoi_RelatedPartyTransactionOwnershipPercentageOfRelatedParty
Namespace Prefix:	ccoi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

Name:	us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Related party transactions: (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Nov. 30, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Lease
Office lease
Payment for rent and related costs (in dollars)		$ 0.6	$ 0.6	$ 0.6
Additional lease term	2 years
Notice period for cancellation of lease		60 days
Headquarters building
Office lease
Number of owners of the LLC		2
Chief Executive Officer \| Headquarters building
Office lease
Ownership interest of related parties held in the partnership (as a percent)		51.00%
Chief Executive Officer's wife \| Headquarters building
Office lease
Ownership interest of related parties held in the partnership (as a percent)		49.00%