Indebtedness - Narrative (Details) $ in Thousands	3 Months Ended
Mar. 31, 2017 USD ($) building property loan
Debt Disclosure [Abstract]
Number of properties secured by mortgage notes \| property	3
Number of buildings secured by mortgage notes \| building	3
Aggregate net book value of secured properties	$ 51,600
Number of assumed secured mortgage loans \| loan	3
Aggregate principal amount on secured properties	$ 27,129

Represents the aggregate net book value of real estate properties serving as a collateral for debt, as of the balance sheet date.

No definition available.

Name:	gov_AggregateNetBookValueOfRealEstatePropertiesCollateralized
Namespace Prefix:	gov_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The aggregate principal amount on real estate properties serving as collateral for debt as of the balance sheet date.

No definition available.

Name:	gov_AggregatePrincipalAmountOfRealEstatePropertiesCollateralized
Namespace Prefix:	gov_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents the number of mortgage loans on real estate assumed in acquisitions during the period.

No definition available.

Name:	gov_MortgageLoansOnRealEstateAssumedInAcquisitionsNumberOfLoans
Namespace Prefix:	gov_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

The number of buildings serving as collateral for debt as of the balance sheet date.

No definition available.

Name:	gov_NumberOfBuildingsCollateralized
Namespace Prefix:	gov_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the number of real estate properties serving as a collateral for debt, as of the balance sheet date.

No definition available.

Name:	gov_NumberOfRealEstatePropertiesCollateralized
Namespace Prefix:	gov_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

No definition available.

Name:	us-gaap_DebtDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration