Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Feb. 23, 2021	Jun. 30, 2020
Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-15319
Entity Registrant Name	DIVERSIFIED HEALTHCARE TRUST
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	04-3445278
Entity Address, Street	Two Newton Place, 255 Washington Street, Suite 300
Entity Address, City	Newton
Entity Address, State	MA
Entity Address, Postal Zip Code	02458-1634
City Area Code	617
Local Phone Number	796-8350
Title of 12(b) Security	Common Shares of Beneficial Interest
Trading Symbol	DHC
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Smaller Reporting Company	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1.0
Entity Common Stock, Shares Outstanding (in shares)		238,268,478
Documents Incorporated by Reference	Certain information required by Items 10, 11, 12, 13 and 14 of Part III of this Annual Report on Form 10-K is incorporated by reference to our definitive Proxy Statement for the 2021 Annual Meeting of Shareholders, to be filed with the Securities and Exchange Commission within 120 days after the fiscal year ended December 31, 2020.
Entity Central Index Key	0001075415
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Senior Notes Due 2042
Entity Information
Title of 12(b) Security	5.625% Senior Notes due 2042
Trading Symbol	DHCNI
Security Exchange Name	NASDAQ
Senior Notes Due 2046
Entity Information
Title of 12(b) Security	6.25% Senior Notes due 2046
Trading Symbol	DHCNL
Security Exchange Name	NASDAQ