Cover - shares	9 Months Ended
	Sep. 30, 2020	Nov. 02, 2020
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
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, Address Line One	Two Newton Place, 255 Washington Street, Suite 300,
Entity Address, City or Town	Newton
Entity Address, State or Province	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 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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		238,268,478
Entity Central Index Key	0001075415
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Senior Notes Due 2042
Entity Information [Line Items]
Title of 12(b) Security	5.625% Senior Notes due 2042
Trading Symbol	DHCNI
Security Exchange Name	NASDAQ
Senior Notes Due 2046
Entity Information [Line Items]
Title of 12(b) Security	6.25% Senior Notes due 2046
Trading Symbol	DHCNL
Security Exchange Name	NASDAQ