Real Estate Properties - Merger With Select Income REIT (Details) $ / shares in Units, $ in Thousands					1 Months Ended
	Jul. 01, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) ft² property	Dec. 27, 2018 shares	Oct. 09, 2018 USD ($) $ / shares shares	Jul. 31, 2019 USD ($)	Aug. 01, 2019 ft²	Jun. 30, 2019 ft²
SIR
Business Acquisition [Line Items]
Number of properties acquired | property		99
Rentable area of properties (in square feet) | ft²		16,500,000
Consideration transferred		$ 2,415,053
Closing costs		27,497
Payments for closing costs		14,508
Debt assumed		1,719,772
SIR | SIR
Business Acquisition [Line Items]
Payments for closing costs		$ 12,989
Underwritten public offering | Common shares
Business Acquisition [Line Items]
Shares sold (in shares) | shares				24,918,421
Price per share (in dollars per share) | $ / shares				$ 18.25
Proceeds from sale of shares				$ 435,125
ILPT | SIR
Business Acquisition [Line Items]
Shares holding (in shares) | shares			45,000,000
Disposal Group, Disposed of by Sale
Business Acquisition [Line Items]
Rentable area of properties (in square feet) | ft²							2,590,607
Subsequent Event
Business Acquisition [Line Items]
Consideration transferred					$ 2,900
Subsequent Event | Underwritten public offering
Business Acquisition [Line Items]
Shares sold (in shares) | shares	2,801,060
Price per share (in dollars per share) | $ / shares	$ 40.00
Proceeds from sale of shares	$ 105,040
Subsequent Event | Disposal Group, Disposed of by Sale
Business Acquisition [Line Items]
Rentable area of properties (in square feet) | ft²						1,113,000