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

No definition available.

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- Definition

This element represents the aggregate sales price excluding closing costs, of real estate properties sold by the entity.

+ References

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Area of a real estate property.

+ References

No definition available.

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- Definition

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

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No definition available.

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- Definition

Amount of gain on the sale of property that does not qualify for gain recognition as of the balance sheet date.

+ References

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

This element represents the amount of gain (loss) on sale of properties during the reporting period net of the applicable income taxes realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-15.(a)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=6875705&loc=d3e641549-123027

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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.

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

- Definition

Mortgage loan related to property sales in noncash investing and financing activities.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
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- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
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Period Type:	instant

- Definition

Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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-SubTopic 210
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-Paragraph 1
-Subparagraph (SX 210.7-03.1(d))
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Details

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- Details

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Period Type:

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Period Type:

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Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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Real Estate Properties - 2016 Dispositions (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2016 USD ($) ft² building property	Mar. 31, 2017	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) ft²	Dec. 31, 2015 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable area of properties (in square feet) \| ft²				830,185
Net book value			$ 2,633,873	$ 1,591,956
Gain on sale of real estate			0	79	$ 0
Deferred gain on sale of real estate			712
One building \| Disposal Group, Held-for-sale \| Savannah, GA \| Office Building
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties owned \| property	1
Number of Buildings \| building	1
Rentable area of properties (in square feet) \| ft²	35,228
Net book value	$ 2,986
Aggregate sale price of properties sold, excluding closing costs	4,000
Mortgage loan	$ 3,600
LIBOR \| Disposal Group, Disposed of by Sale \| Savannah, GA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Basis spread on variable rate		4.00%
Minimum \| LIBOR \| Disposal Group, Disposed of by Sale \| Savannah, GA
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Basis spread on variable rate		5.00%
Other Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred gain on sale of real estate			712	$ 712
Real Estate Loan \| Other Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Financing receivable			$ 3,600