Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Aug. 07, 2019
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	1-15319
Document Period End Date	Jun. 30, 2019
Amendment Flag	false
Entity Registrant Name	SENIOR HOUSING PROPERTIES TRUST
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
Entity Incorporation, State or Country Code	MD
City Area Code	617
Local Phone Number	796 - 8350
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Shares of Beneficial Interest
Trading Symbol	SNH
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding (in shares)		237,737,849
Entity Central Index Key	0001075415
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Emerging Growth Company	false
Entity Smaller Reporting Company	false
Entity Shell Company	false
Senior Notes Due 2042
Document Information [Line Items]
Title of 12(b) Security	5.625% Senior Notes due 2042
Trading Symbol	SNHNI
Security Exchange Name	NASDAQ
Senior Notes Due 2046
Document Information [Line Items]
Title of 12(b) Security	6.25% Senior Notes due 2046
Trading Symbol	SNHNL
Security Exchange Name	NASDAQ