Document and Entity Information Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 21, 2020	Jun. 30, 2019
Document Information [Line Items]
Document Annual Report	true
Entity Central Index Key	0000826675
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Incorporation, State or Country Code	VA
Entity Tax Identification Number	52-1549373
Document Transition Report	false
Current Fiscal Year End Date	--12-31
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity File Number	1-9819
Entity Registrant Name	DYNEX CAPITAL, INC.
Entity Address, Address Line One	4991 Lake Brook Drive,
Entity Address, Address Line Two	Suite 100
Entity Address, City or Town	Glen Allen,
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	23060-9245
City Area Code	(804)
Local Phone Number	217-5800
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		22,945,993
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Public Float			$ 398,195,573
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $.01 par value
Trading Symbol	DX
Security Exchange Name	NYSE
Series A Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	8.50% Series A Cumulative Redeemable Preferred Stock, par value $0.01 per share
Trading Symbol	DXPRA
Security Exchange Name	NYSE
Series B Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	7.625% Series B Cumulative Redeemable Preferred Stock, par value $0.01 per share
Trading Symbol	DXPRB
Security Exchange Name	NYSE
Series C Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	6.90% Series C Fixed-to-Floating Rate Cumulative Redeemable Preferred Stock, par value $0.01 per share
Trading Symbol	DXPRC
Security Exchange Name	NYSE