Annual report pursuant to Section 13 and 15(d)

Consolidated Statement of Cash Flows Supplemental Disclosures ( Non-cash investing and financing activities) (Details)

v2.4.1.9
Consolidated Statement of Cash Flows Supplemental Disclosures ( Non-cash investing and financing activities) (Details) (USD $)
In Thousands, unless otherwise specified
 0 Months Ended 12 Months Ended
Jan. 01, 2014
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Supplemental Cash Flow Elements [Abstract]        
Non-cash additions for purchases of property and equipment   $ 42,958us-gaap_CapitalExpendituresIncurredButNotYetPaid $ 17,230us-gaap_CapitalExpendituresIncurredButNotYetPaid $ 9,010us-gaap_CapitalExpendituresIncurredButNotYetPaid
Capital lease obligation incurred 9,400us-gaap_CapitalLeaseObligationsIncurred 9,386us-gaap_CapitalLeaseObligationsIncurred 0us-gaap_CapitalLeaseObligationsIncurred 0us-gaap_CapitalLeaseObligationsIncurred
Asset retirement obligation additions to property and equipment   4,268us-gaap_AssetRetirementObligationLiabilitiesIncurred 5,292us-gaap_AssetRetirementObligationLiabilitiesIncurred 660us-gaap_AssetRetirementObligationLiabilitiesIncurred
Accrued distribution to non-controlling interest   4,167gncma_DistributiontoNoncontrollingInterest 4,167gncma_DistributiontoNoncontrollingInterest 0gncma_DistributiontoNoncontrollingInterest
Deferred compensation distribution denominated in shares   617us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationGiven1 621us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationGiven1 511us-gaap_OtherSignificantNoncashTransactionValueOfConsiderationGiven1
Net assets acquired with equity in AWN (see Note 1(d))   $ 0us-gaap_NoncashOrPartNoncashAcquisitionOtherAssetsAcquired1 $ 267,642us-gaap_NoncashOrPartNoncashAcquisitionOtherAssetsAcquired1 $ 0us-gaap_NoncashOrPartNoncashAcquisitionOtherAssetsAcquired1