v2.4.0.8
Document and Entity Information (USD $)
12 Months Ended
Dec. 31, 2014
Jun. 30, 2014
Jan. 31, 2015
Class A Common Stock
Jan. 31, 2015
Class B Convertible Common Stock
Entity Information [Line Items]        
Document Type 10-K      
Amendment Flag false      
Document Period End Date Dec. 31, 2014      
Document Fiscal Year Focus 2014      
Document Fiscal Period Focus FY      
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     177,312,580 36,600,000
Entity Well-known Seasoned Issuer Yes      
Entity Voluntary Filers No      
Entity Current Reporting Status Yes      
Entity Public Float   $ 10,314,358,804