v3.5.0.2
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2016
Dec. 31, 2015
Sep. 30, 2015
Entity Information [Line Items]      
Document Type 10-Q    
Amendment Flag false    
Document Period End Date Sep. 30, 2016    
Document Fiscal Year Focus 2016    
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    
Class A Common Stock [Member]      
Entity Information [Line Items]      
Entity Common Stock, Shares Outstanding 183,739,248    
Common Stock, Shares, Issued 183,739,248 181,646,468 180,115,884
Common Stock, Shares Authorized 400,000,000 400,000,000 400,000,000
Class B Convertible Common Stock [Member]      
Entity Information [Line Items]      
Entity Common Stock, Shares Outstanding 34,450,000    
Common Stock, Shares, Issued 34,450,000 34,450,000 35,700,000
Common Stock, Shares Authorized 34,450,000 34,450,000 35,700,000
Common Class C [Member]      
Entity Information [Line Items]      
Entity Common Stock, Shares Outstanding 219,963,397    
Common Stock, Shares, Issued 219,963,397 216,096,468 215,815,884
Common Stock, Shares Authorized 400,000,000 400,000,000 400,000,000