Business Combination, Common Stock, Share Conversion Ratio

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Number Of Joint Ventures

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Number Of Properties

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Number Of Properties Acquired

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The number of states in which real estate owned by the entity is located as of the balance sheet date.

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Payments For Business Acquisition Costs

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Area of a real estate property.

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Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

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Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The cash inflow from the issuance of common stock, preferred stock, treasury stock, stock options, and other types of equity.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

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Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

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Cumulative number of shares issued or sold by the subsidiary or equity method investee on all stock transactions.

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Organization (Details) $ / shares in Units, $ in Thousands, ft² in Millions						12 Months Ended
	Dec. 31, 2018 USD ($) ft² $ / shares shares	Dec. 27, 2018 shares	Oct. 09, 2018 USD ($) $ / shares shares	Oct. 02, 2017 USD ($) ft² property joint_venture	Jul. 05, 2017 $ / shares shares	Dec. 31, 2019 USD ($) ft² property state joint_venture	Dec. 31, 2018 USD ($) ft² property $ / shares shares	Dec. 31, 2017 USD ($)
Real Estate Properties [Line Items]
Number of joint ventures \| joint_venture						2
Proceeds from sale of The RMR Group Inc. common shares, net						$ 104,674	$ 0	$ 0
Stock split conversion ratio	0.25
Continuing Operations
Real Estate Properties [Line Items]
Number of properties \| property						189
Number of states in which owned properties located \| state						35
Rentable area of properties (in square feet) \| ft²						25.7
First Potomac Realty Trust
Real Estate Properties [Line Items]
Rentable area of properties (in square feet) \| ft²				6.0		0.4
Number of properties acquired \| property				72
Total consideration transferred and liabilities assumed				$ 1,370,888
Liabilities assumed				$ 483,000
SIR
Real Estate Properties [Line Items]
Rentable area of properties (in square feet) \| ft²	16.5						16.5
Number of properties acquired \| property							99
Share price (in dollars per share) \| $ / shares	$ 6.87						$ 6.87
Total consideration transferred and liabilities assumed							$ 2,409,740
Transaction costs	$ 27,497						27,497
Payment transaction costs	$ 14,508
Liabilities assumed							$ 1,719,772
Share conversion ratio (in shares) \| shares	1.04						1.04
Common Shares \| SIR
Real Estate Properties [Line Items]
Share price (in dollars per share) \| $ / shares	$ 27.48						$ 27.48
Underwritten Public Offering
Real Estate Properties [Line Items]
Number of shares sold (in shares) \| shares					6,250,000
Sale of stock (in dollars per share) \| $ / shares					$ 74.00
Underwritten Public Offering \| Common Shares
Real Estate Properties [Line Items]
Number of shares sold (in shares) \| shares			24,918,421
Sale of stock (in dollars per share) \| $ / shares			$ 18.25
Proceeds from sale of The RMR Group Inc. common shares, net			$ 435,125
First Potomac Realty Trust
Real Estate Properties [Line Items]
Number of properties \| property				3		3
Number of joint ventures \| joint_venture				2		2
First Potomac Realty Trust \| First Potomac Realty Trust
Real Estate Properties [Line Items]
Rentable area of properties (in square feet) \| ft²				0.4
SIR
Real Estate Properties [Line Items]
Payment transaction costs	$ 12,989
Joint Venture Property 1
Real Estate Properties [Line Items]
Percentage of ownership interest						50.00%
Joint Venture Property 1 \| First Potomac Realty Trust
Real Estate Properties [Line Items]
Percentage of ownership interest				50.00%		51.00%
Joint Venture Property 2
Real Estate Properties [Line Items]
Percentage of ownership interest						51.00%
Joint Venture Property 2 \| First Potomac Realty Trust
Real Estate Properties [Line Items]
Percentage of ownership interest				51.00%		50.00%
Industrial Logistics Properties Trust \| SIR
Real Estate Properties [Line Items]
Shares owned (in shares) \| shares		45,000,000