v2.4.0.8
Document and Entity Information
9 Months Ended
Sep. 30, 2013
Oct. 31, 2013
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  
Entity Registrant Name American Capital Agency Corp  
Entity Central Index Key 0001423689  
Entity Filer Category Large Accelerated Filer  
Current Fiscal Year End Date --12-31  
Entity Common Stock, Shares Outstanding   396,451,470
Trading Symbol AGNC  
Entity Well-known Seasoned Issuer Yes  
Entity Voluntary Filers No  
Entity Current Reporting Status Yes