Document and Entity Information
9 Months Ended
Sep. 30, 2010
Oct. 22, 2010
Document and Entity Information    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2010  
Document Fiscal Year Focus 2010  
Document Fiscal Period Focus Q3  
Entity Registrant Name AMERICAN TOWER CORP /MA/  
Entity Central Index Key 0001053507  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   399,079,954