Document and Entity Information - USD ($)	9 Months Ended
	Sep. 30, 2015	Oct. 28, 2015	Jun. 30, 2014
Entity Information [Line Items]
Entity Registrant Name	DYNEX CAPITAL INC
Entity Central Index Key	0000826675
Current Fiscal Year End Date	--12-31
Entity Filer Category	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		49,168,790
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 448,865,442