| **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 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319
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| X                                                                                                                                                                       |
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| X                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                              |
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