Document and Entity Information	9 Months Ended
	Sep. 30, 2015 shares
Entity [Abstract]
Entity Registrant Name	FEDERAL NATIONAL MORTGAGE ASSOCIATION FANNIE MAE
Entity Central Index Key	0000310522
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding	1,158,082,750