Concentration (Details)	6 Months Ended
Jun. 30, 2016 state property building item	Jun. 30, 2015 property building
Concentration
Number of properties \| property	72
Number of buildings \| building	92
Number of states in which acquired properties located \| state	31
Number of state governments \| state	12
Number of other governments \| item	3
Annualized rental income, excluding properties classified as discontinued operations \| California
Concentration
Annualized Rental income percent	14.7
Annualized rental income, excluding properties classified as discontinued operations \| Virginia
Concentration
Annualized Rental income percent	10.0
Annualized rental income, excluding properties classified as discontinued operations \| District of Columbia
Concentration
Annualized Rental income percent	9.9
Annualized rental income, excluding properties classified as discontinued operations \| Georgia
Concentration
Annualized Rental income percent	9.2
Annualized rental income, excluding properties classified as discontinued operations \| New York
Concentration
Annualized Rental income percent	8.1
Annualized rental income, excluding properties classified as discontinued operations \| Maryland
Concentration
Annualized Rental income percent	7.6
Annualized rental income, excluding properties classified as discontinued operations \| Massachusetts
Concentration
Annualized Rental income percent	5.3
Annualized rental income, excluding properties classified as discontinued operations \| Tenant concentration \| U.S. Government, state governments and Other Three Government
Concentration
Concentration risk, percentage	92.70%	92.80%
Annualized rental income, excluding properties classified as discontinued operations \| Tenant concentration \| U.S. Government
Concentration
Concentration risk, percentage	64.10%	67.70%
Discontinued operations
Concentration
Number of properties \| property	1	1
Number of buildings \| building	1	1

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

No definition available.

Name:	gov_NumberOfBuildings
Namespace Prefix:	gov_
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Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	gov_NumberOfOtherGovernments
Namespace Prefix:	gov_
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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_
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Balance Type:	na
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- 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_
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- 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
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- 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

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=51801978&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=51801978&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13537-108611

+ Details

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Data Type:	num:percentItemType
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

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- Details

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- Details

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- Details

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