The number of buildings owned as of the balance sheet date.

No definition available.

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

- Definition

Represents the number of state governments that are tenants of the entity.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

This element represents the percentage of rental income in each state.

+ References

No definition available.

+ Details

Name:	gov_RealEstateRevenuePercent
Namespace Prefix:	gov_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_ConcentrationRiskByBenchmarkAxis=gov_RealEstateRevenueNetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=stpr_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=stpr_VA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=stpr_DC
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=stpr_GA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=stpr_NY
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=stpr_MD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=stpr_MA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorCustomersAxis=gov_USGovernmentStateGovernmentsAndUnitedNationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorCustomersAxis=gov_USGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementOperatingActivitiesSegmentAxis=us-gaap_SegmentDiscontinuedOperationsMember
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Concentration (Details)	12 Months Ended
Concentration (Details)	Dec. 31, 2015 state property building	Dec. 31, 2014 state	Dec. 31, 2013
Concentration
Number of properties owned \| property	71
Number of buildings \| building	91
Number of states in which acquired properties located \| state	31
Number of state governments \| state		12
Annualized rental income, excluding properties classified as discontinued operations \| California
Concentration
Annualized Rental income percent	11.400
Annualized rental income, excluding properties classified as discontinued operations \| Virginia
Concentration
Annualized Rental income percent	10.400
Annualized rental income, excluding properties classified as discontinued operations \| District of Columbia
Concentration
Annualized Rental income percent	10.200
Annualized rental income, excluding properties classified as discontinued operations \| Georgia
Concentration
Annualized Rental income percent	8.60
Annualized rental income, excluding properties classified as discontinued operations \| New York
Concentration
Annualized Rental income percent	8.60
Annualized rental income, excluding properties classified as discontinued operations \| Maryland
Concentration
Annualized Rental income percent	8.40
Annualized rental income, excluding properties classified as discontinued operations \| Massachusetts
Concentration
Annualized Rental income percent	5.60
Annualized rental income, excluding properties classified as discontinued operations \| Tenant concentration \| U.S. Government, state governments and the United Nations
Concentration
Annualized Rental income percent	92.8	93.0	92.6
Annualized rental income, excluding properties classified as discontinued operations \| Tenant concentration \| U.S. Government
Concentration
Annualized Rental income percent	67.0	69.0	69.0
Discontinued operations
Concentration
Number of properties owned \| property	1
Number of buildings \| building	1