Annual report pursuant to Section 13 and 15(d)

Income Taxes (Summary of tax net operating loss carryforwards) (Details)

v2.4.1.9
Income Taxes (Summary of tax net operating loss carryforwards) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Federal  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards $ 320,250us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
Federal | 2020  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 34,958us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearOneMember
Federal | 2021  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 29,614us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearTwoMember
Federal | 2022  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 14,081us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearThreeMember
Federal | 2023  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 3,968us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearFourMember
Federal | 2024  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 722us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearFiveMember
Federal | 2025  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 737us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearSixMember
Federal | 2026  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 150us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearSevenMember
Federal | 2027  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 1,010us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearEightMember
Federal | 2028  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 39,879us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearNineMember
Federal | 2029  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 48,370us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearTenMember
Federal | 2031  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 110,933us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearTwelveMember
Federal | 2033  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 5,031us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearThirteenMember
Federal | 2034  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 30,797us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_DomesticCountryMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearFourteenMemberMember
State  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 312,501us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
State | 2020  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 34,301us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearOneMember
State | 2021  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 28,987us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearTwoMember
State | 2022  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 13,788us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearThreeMember
State | 2023  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 3,903us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearFourMember
State | 2024  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 0us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearFiveMember
State | 2025  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 0us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearSixMember
State | 2026  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 0us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearSevenMember
State | 2027  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 0us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearEightMember
State | 2028  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 39,715us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearNineMember
State | 2029  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 47,558us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearTenMember
State | 2031  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 109,376us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearTwelveMember
State | 2033  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards 4,927us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearThirteenMember
State | 2034  
Operating Loss Carryforwards [Line Items]  
Net operating loss carryforwards $ 29,946us-gaap_OperatingLossCarryforwards
/ us-gaap_IncomeTaxAuthorityAxis
= us-gaap_StateAndLocalJurisdictionMember
/ gncma_LossCarryforwardsYearAxis
= gncma_LossCarryforwardInYearFourteenMemberMember