v2.4.0.8
Document and Entity Information
9 Months Ended
Sep. 30, 2013
Oct. 31, 2013
Class A Common Stock [Member]
Oct. 31, 2013
Class B Convertible Common Stock [Member]
Entity Information [Line Items]      
Document Type 10-Q    
Amendment Flag false    
Document Period End Date Sep. 30, 2013    
Document Fiscal Year Focus 2013    
Document Fiscal Period Focus Q3    
Trading Symbol UA    
Entity Registrant Name UNDER ARMOUR, INC.    
Entity Central Index Key 0001336917    
Current Fiscal Year End Date --12-31    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   85,633,439 20,000,000