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Summarized Financial Information of Subsidiaries - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Debt Instrument [Line Items]    
Balance of permitted transfers to parent company $ 2,269,393lamr_BalanceOfPermittedTransfersToParentCompany $ 2,072,542lamr_BalanceOfPermittedTransfersToParentCompany
Description of provisions on senior credit facility transfers to Lamar Advertising not subject to additional restrictions (i) the total debt ratio is equal to or greater than 6.0 to 1 or (ii) the senior debt ratio is equal to or greater than 3.5 to 1.  
Debt ratio 6.0lamr_MinimumHoldingDebtRatioForApplicabilityOfRestrictionOnTransfer  
Description of actual position on senior credit facility transfers to Lamar Advertising not subject to additional restrictions The total debt ratio was less than 6.0 to 1 and Lamar Media's senior debt ratio was less than 3.5 to 1; therefore, dividends or distributions to Lamar Advertising were not subject to any additional restrictions under the senior credit facility.  
Debt ratio related to actual position on senior credit facility 6.0lamr_MaximumActualHoldingsDebtRatio  
Senior Credit Facility [Member]    
Debt Instrument [Line Items]    
Senior debt ratio 3.5us-gaap_RatioOfIndebtednessToNetCapital1
/ us-gaap_LongtermDebtTypeAxis
= lamr_SeniorCreditAgreementMember		  
Senior Subordinated Notes [Member] | Maximum [Member]    
Debt Instrument [Line Items]    
Senior debt ratio 3.5us-gaap_RatioOfIndebtednessToNetCapital1
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorSubordinatedNotesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember