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Retirement Plan - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended 8 Months Ended 27 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]          
Defined benefit plan matching contributions amount $ 1.0us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount $ 0.7us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount $ 0.3us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount    
First Eligible Contribution Percentage          
Defined Benefit Plan Disclosure [Line Items]          
Companies matching on eligible employee contribution percentage       67.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
/ us-gaap_StatementScenarioAxis
= grub_ScenarioOneMember		 100.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
/ us-gaap_StatementScenarioAxis
= grub_ScenarioOneMember
Defined benefit plan eligible employee percentage       6.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
/ us-gaap_StatementScenarioAxis
= grub_ScenarioOneMember		 3.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
/ us-gaap_StatementScenarioAxis
= grub_ScenarioOneMember
Second Eligible Contribution Percentage          
Defined Benefit Plan Disclosure [Line Items]          
Companies matching on eligible employee contribution percentage         50.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
/ us-gaap_StatementScenarioAxis
= grub_ScenarioTwoMember
Defined benefit plan eligible employee percentage         2.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
/ us-gaap_StatementScenarioAxis
= grub_ScenarioTwoMember