Represents the information pertaining to estimated termination liability in terminating capital lease obligations.

No definition available.

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Period Type:	duration

- Definition

Represents the fair market value of the equipment received in exchange of old equipment.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Represents the gain (loss) resulted from asset exchange transactions.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Represents the number of equal payments on note obligation.

+ References

No definition available.

+ Details

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Namespace Prefix:	ccoi_
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Balance Type:	na
Period Type:	duration

- Definition

Represents the remaining term for the note obligation, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Represents the number of payments during the first six months of the note obligation.

+ References

No definition available.

+ Details

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

- Definition

Represents the compensation costs the entity capitalizes as a part of property, plant and equipment.

+ References

No definition available.

+ Details

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

- Definition

Period of time relating to the maturity of the purchase agreement, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Namespace Prefix:	ccoi_
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Balance Type:	na
Period Type:	duration

- Definition

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

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-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 30

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-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

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Balance Type:	debit
Period Type:	instant

- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

+ References

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

-Publisher FASB

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-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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Balance Type:	debit
Period Type:	duration

- Definition

Gain (loss) related to the termination of a contract between the parties. The termination may be due to many causes including early termination of a lease by a lessee, a breach of contract by one party, or a failure to perform.

+ References

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

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-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

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Balance Type:	credit
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- Details

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- Definition

Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Minimum amount to be expended to satisfy the terms of arrangements in which the entity has agreed to expend funds to procure goods or services, excluding long-term purchase commitments or unconditional purchase obligations.

+ References

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

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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Balance Type:	credit
Period Type:	instant

- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

Name:	us-gaap_PurchaseObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Period Type:	duration

- Definition

Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25383-109308

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- Details

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Property and equipment: (Details) (USD $)	3 Months Ended		1 Months Ended
Property and equipment: (Details) (USD $)	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Jan. 31, 2015	Dec. 31, 2014
Property and equipment
Depreciation and amortization expense	$ 17,513,000	$ 17,204,000
Capitalized salaries and related benefits of employees	2,200,000	2,000,000
Gains from asset related transactions	3,956,000	2,235,000
Gain on capital lease termination
Net book value	343,429,000us-gaap_PropertyPlantAndEquipmentNet		343,429,000us-gaap_PropertyPlantAndEquipmentNet		360,761,000us-gaap_PropertyPlantAndEquipmentNet
Gain on capital lease termination	10,110,000us-gaap_GainLossOnContractTermination
Vendor in Spain
Gain on capital lease termination
Estimated termination liability of IRU capital leases			8,100,000
Carrying value of lease liabilities	29,900,000		29,900,000
Gain on capital lease termination			10,100,000
Property, equipment and capital leases
Property and equipment
Depreciation and amortization expense	17,500,000	17,100,000
Network equipment
Property and equipment
Gains from asset related transactions	1,500,000	2,200,000
Equipment purchase agreement
Purchase agreement				28,900,000
Term of purchase agreement				18 months
Required purchases remaining under purchase agreement	26,600,000		26,600,000
Network equipment \| Note obligations
Property and equipment
Number of payments during the first six months	0
Number of equal payments	18
Remaining term	18 months
Installment payment agreement
Amount of installment payment agreement	25,000,000		25,000,000
Term of debt			24 months
Aggregate principal amount of debt issued	1,700,000		1,700,000
Unamortized discount	100,000		100,000
Network equipment \| Level 3
Property and equipment
Fair market value of equipment received in exchange	6,600,000	4,700,000
Indefeasible rights of use (IRUs) \| Vendor in Spain
Gain on capital lease termination
Net book value	$ 10,000,000		$ 10,000,000