Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 19, 2020	Jun. 28, 2019
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-34364
Entity Registrant Name	OFFICE PROPERTIES INCOME TRUST
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	26-4273474
Entity Address, Address Line One	Two Newton Place
Entity Address, Address Line Two	255 Washington Street
Entity Address, Address Line Three	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	219-1440
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 Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1.2
Entity Common Stock, Shares Outstanding		48,201,531
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 2020 Annual Meeting of Shareholders, to be filed with the Securities and Exchange Commission within 120 days after the fiscal year ended December 31, 2019.
Entity Central Index Key	0001456772
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Common Shares
Document Information [Line Items]
Title of 12(b) Security	Common Shares of Beneficial Interest
Trading Symbol	OPI
Security Exchange Name	NASDAQ
5.875% Senior Notes Due 2046
Document Information [Line Items]
Title of 12(b) Security	5.875% Senior Notes due 2046
Trading Symbol	OPINI
Security Exchange Name	NASDAQ