Quarterly report pursuant to Section 13 or 15(d)

Segments (Reconciliation of reportable segment adjusted EBITDA) (Details)

v2.4.1.9
Segments (Reconciliation of reportable segment adjusted EBITDA) (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Segment Reporting Information [Line Items]    
Reportable segment Adjusted EBITDA $ 75,303gncma_IncomeLossfromContinuingOperationsbeforeEquityMethodInvestmentsIncomeTaxesAdjusted $ 74,797gncma_IncomeLossfromContinuingOperationsbeforeEquityMethodInvestmentsIncomeTaxesAdjusted
Less depreciation and amortization expense (45,235)us-gaap_DepreciationDepletionAndAmortization (42,352)us-gaap_DepreciationDepletionAndAmortization
Less share-based compensation expense (2,801)us-gaap_ShareBasedCompensation (1,778)us-gaap_ShareBasedCompensation
Other (3,147)us-gaap_OtherNonoperatingIncomeExpense (97)us-gaap_OtherNonoperatingIncomeExpense
Operating income 741us-gaap_OperatingIncomeLoss 30,265us-gaap_OperatingIncomeLoss
Less other expense, net (26,252)us-gaap_NonoperatingIncomeExpense (18,308)us-gaap_NonoperatingIncomeExpense
Income before income tax expense (25,511)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments 11,957us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Segment Reconciling Items [Member]    
Segment Reporting Information [Line Items]    
Reportable segment Adjusted EBITDA 75,303gncma_IncomeLossfromContinuingOperationsbeforeEquityMethodInvestmentsIncomeTaxesAdjusted
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
74,797gncma_IncomeLossfromContinuingOperationsbeforeEquityMethodInvestmentsIncomeTaxesAdjusted
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
Less depreciation and amortization expense (45,235)us-gaap_DepreciationDepletionAndAmortization
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
(42,352)us-gaap_DepreciationDepletionAndAmortization
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
Software write-off (26,417)us-gaap_ResearchAndDevelopmentExpenseSoftwareExcludingAcquiredInProcessCost
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
0us-gaap_ResearchAndDevelopmentExpenseSoftwareExcludingAcquiredInProcessCost
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
Less share-based compensation expense (2,801)us-gaap_ShareBasedCompensation
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
(1,778)us-gaap_ShareBasedCompensation
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
Less accretion expense (450)us-gaap_AssetRetirementObligationAccretionExpense
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
(301)us-gaap_AssetRetirementObligationAccretionExpense
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
Other 341us-gaap_OtherNonoperatingIncomeExpense
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
(101)us-gaap_OtherNonoperatingIncomeExpense
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
Operating income 741us-gaap_OperatingIncomeLoss
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
30,265us-gaap_OperatingIncomeLoss
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
Less other expense, net (26,252)us-gaap_NonoperatingIncomeExpense
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
(18,308)us-gaap_NonoperatingIncomeExpense
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
Income before income tax expense $ (25,511)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember
$ 11,957us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
/ us-gaap_ConsolidationItemsAxis
= us-gaap_MaterialReconcilingItemsMember