v2.4.0.6
Document and Entity Information
3 Months Ended
Sep. 30, 2012
Oct. 31, 2012
Entity Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2012  
Document Fiscal Year Focus 2012  
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   341,598,550
Trading Symbol AGNC