Annual report pursuant to Section 13 and 15(d)

Net Property and Equipment in Service (Details)

v2.4.1.9
Net Property and Equipment in Service (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 2,242,271gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress $ 2,053,854gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
Less accumulated depreciation 1,178,982gncma_AccumulatedDepreciationPropertyPlantandEquipment 1,042,724gncma_AccumulatedDepreciationPropertyPlantandEquipment
Less accumulated amortization 50,047gncma_AccumulatedAmortizationPropertyPlantandEquipment 41,552gncma_AccumulatedAmortizationPropertyPlantandEquipment
Net property and equipment in service 1,013,242gncma_PropertyandEquipmentinServiceNet 969,578gncma_PropertyandEquipmentinServiceNet
Property and equipment under capital leases 112,495us-gaap_CapitalLeasedAssetsGross 104,251us-gaap_CapitalLeasedAssetsGross
Land and buildings    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 100,038gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandAndBuildingMember
69,984gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandAndBuildingMember
Telephony transmission equipment and distribution facilities    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 1,189,470gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_TelephonyTransmissionEquipmentAndDistributionFacilitiesMember
1,085,963gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_TelephonyTransmissionEquipmentAndDistributionFacilitiesMember
Cable transmission equipment and distribution facilities    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 193,832gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_CableTransmissionEquipmentandDistributionFacilitiesMember
177,410gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_CableTransmissionEquipmentandDistributionFacilitiesMember
Studio equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 14,396gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_StudioEquipmentMember
12,680gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_StudioEquipmentMember
Support equipment and systems    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 270,629gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_SupportEquipmentAndSystemMember
245,301gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_SupportEquipmentAndSystemMember
Transportation equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 15,667gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_TransportationEquipmentMember
13,619gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_TransportationEquipmentMember
Customer premise equipment    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross 153,039gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_EquipmentLeasedToOtherPartyMember
149,372gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_EquipmentLeasedToOtherPartyMember
Fiber optic cable systems    
Property, Plant and Equipment [Line Items]    
Property, plant and equipment, gross $ 305,200gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_FiberOpticCableSystemsMember
$ 299,525gncma_PropertyPlantandEquipmentGrossExcludingConstructioninProgress
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= gncma_FiberOpticCableSystemsMember