The aggregate net book value of real estate properties serving as 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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The option to extend the maturity date subject to certain conditions and the payment of a fee under the credit facility.

+ References

No definition available.

+ Details

Name:	gov_DebtInstrumentContingentOptionToExtendMaturityDate
Namespace Prefix:	gov_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents maximum borrowing capacity under the debt instrument that may be increased under certain conditions.

+ References

No definition available.

+ Details

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

- Definition

Represents the premium percent charged against the amount repaid for unsecured term loan prior to November 21, 2016.

+ References

No definition available.

+ Details

Name:	gov_LoanPrepaymentPremiumOne
Namespace Prefix:	gov_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the premium percent charged against the amount repaid for unsecured term loan subsequent to November 21, 2016.

+ References

No definition available.

+ Details

Name:	gov_LoanPrepaymentPremiumTwo
Namespace Prefix:	gov_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

The number of real estate properties serving as collateral for debt as of the balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Represents the calculation of the average interest rate weighted by the amount of long-term debt outstanding by type or by instrument at that time.

+ References

No definition available.

+ Details

Name:	gov_WeightedAverageAnnualInterestRate
Namespace Prefix:	gov_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 20, 22
-Article 5

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

No definition available.

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

+ Details

Name:	us-gaap_SecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16(a))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_SeniorNotes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

+ Details

Name:	us-gaap_UnsecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gov_UnsecuredDebtDueIn2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gov_UnsecuredDebtDueIn2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gov_SeniorSecuredNote3.75PercentDueIn2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gov_MortgageNote5.55PercentDueIn2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gov_MortgageNote6.21PercentDueIn2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gov_MortgageNote5.88PercentDueIn2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gov_MortgageNote7PercentDueIn2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=gov_MortgageNote8.15PercentDueIn2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Indebtedness (Details) $ in Thousands	1 Months Ended		3 Months Ended
Indebtedness (Details) $ in Thousands	Mar. 31, 2016 USD ($) property building item	Feb. 29, 2016 USD ($) property building	Mar. 31, 2016 USD ($) property building item loan	Mar. 31, 2015	Apr. 26, 2016 USD ($)	Dec. 31, 2015 USD ($)
Indebtedness
Unsecured revolving credit facility	$ 311,000		$ 311,000			$ 117,000
Unsecured term loans, net	546,660		546,660			546,490
Senior Notes	346,095		346,095			345,809
Mortgage notes payable, net	29,053		29,053			$ 136,299
Maximum borrowing capacity on debt instruments may be increased under certain conditions	$ 2,500,000		2,500,000
Gain (Loss) on early extinguishment of debt			$ 104
Number of properties secured by mortgage notes \| property	3		3
Number of buildings secured by mortgage notes \| item	3		3
Aggregate net book value of secured properties	$ 54,684		$ 54,684
Number of assumed secured mortgage loans \| loan			3
Aggregate principal amount on secured properties	28,592		$ 28,592
Unsecured revolving credit facility
Indebtedness
Unsecured revolving credit facility	$ 311,000		$ 311,000		$ 303,000
Interest rate (as a percent)	1.60%		1.60%
Maximum borrowing capacity on revolving credit facility	$ 750,000		$ 750,000
Option to extend the maturity date subject to certain conditions and the payment of a fee			1 year
The weighted average annual interest rate (as a percent)			1.60%	2.00%
Term loan, interest rate basis			LIBOR
Interest rate premium (as a percent)			1.25%
Facility fee (as a percent)			0.25%
Unsecured term loan, due in 2020
Indebtedness
Face amount	$ 300,000		$ 300,000
Interest rate (as a percent)	1.80%		1.80%
The weighted average annual interest rate (as a percent)			1.80%	1.60%
Term loan, interest rate basis			LIBOR
Interest rate premium (as a percent)			1.40%
Unsecured term loan, due in 2022
Indebtedness
Face amount	$ 250,000		$ 250,000
Interest rate (as a percent)	2.20%		2.20%
The weighted average annual interest rate (as a percent)			2.20%	2.00%
Term loan, interest rate basis			LIBOR
Interest rate premium (as a percent)			1.80%
Loan prepayment premium prior to November 21, 2016 (as a percent)			1.00%
Loan prepayment premium subsequent to November 21, 2016 (as a percent)			0.00%
3.75% Senior unsecured note due In 2019
Indebtedness
Face amount	$ 350,000		$ 350,000
Interest rate (as a percent)	3.75%		3.75%			3.75%
5.55% Mortgage notes due in 2016
Indebtedness
Interest rate (as a percent)	5.55%		5.55%			5.55%
Mortgage note repaid	$ 83,000
Gain (Loss) on early extinguishment of debt	$ 125
Number of properties secured by mortgage notes \| property	1		1
Number of buildings secured by mortgage notes \| building	2		2
6.21% Mortgage notes due in 2016
Indebtedness
Interest rate (as a percent)	6.21%	6.21%	6.21%			6.21%
Mortgage note repaid		$ 23,473
Gain (Loss) on early extinguishment of debt			$ (21)
Number of properties secured by mortgage notes \| property		1
Number of buildings secured by mortgage notes \| building		1
5.88% Mortgage notes due in 2021
Indebtedness
Interest rate (as a percent)	5.88%		5.88%			5.88%
7% Mortgage notes due in 2019
Indebtedness
Interest rate (as a percent)	7.00%		7.00%			7.00%
8.15% Mortgage notes due in 2021
Indebtedness
Interest rate (as a percent)	8.15%		8.15%			8.15%