Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 25, 2019	Jun. 30, 2018	Dec. 31, 2017
Entity Information [Line Items]
Entity Public Float			$ 356,954,131
Entity Registrant Name	DYNEX CAPITAL INC
Entity Central Index Key	0000826675
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Common Stock, Shares Outstanding		70,818,525
Entity Current Reporting Status	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Common stock, par value	$ 0.01			$ 0.01