Rental Property - Summary (Details) $ in Thousands	Sep. 30, 2017 USD ($) building	Dec. 31, 2016 USD ($) building
Property Subject to or Available for Operating Lease [Line Items]
Rental property, net	$ 2,520,630	$ 2,116,836
Number of properties \| building	347
Land
Property Subject to or Available for Operating Lease [Line Items]
Rental property, net	$ 321,365	272,162
Building
Property Subject to or Available for Operating Lease [Line Items]
Rental property, net	1,695,332	1,408,406
Rental property, accumulated depreciation	152,575	125,971
Tenant improvements
Property Subject to or Available for Operating Lease [Line Items]
Rental property, net	30,895	24,974
Rental property, accumulated depreciation	32,075	28,388
Building and land improvements
Property Subject to or Available for Operating Lease [Line Items]
Rental property, net	134,607	107,463
Rental property, accumulated depreciation	49,699	33,054
Construction in progress
Property Subject to or Available for Operating Lease [Line Items]
Rental property, net	19,516	9,298
Deferred leasing intangibles
Property Subject to or Available for Operating Lease [Line Items]
Rental property, net	318,915	294,533
Rental property, accumulated depreciation	$ 273,602	$ 237,456
Other Property [Member]
Property Subject to or Available for Operating Lease [Line Items]
Number of properties \| building	1	1

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

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- Definition

The amount of accumulated depreciation, by major property class, recorded on property subject to or available for lease as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6454179&loc=d3e41551-112718

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6453916&loc=d3e41460-112716

+ Details

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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

The amount of property, by major property class, net of accumulated depreciation, subject to or available for lease as of the balance sheet date.

+ References

+ Details

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