Investments in Real Estate and Real Estate Under Construction - Summary of acquisitions and build-to-suit transactions (Details) $ in Thousands	9 Months Ended
Sep. 30, 2015 USD ($)
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial cost basis	$ 229,558
Land and land estate	25,175
Building and improvements	172,254
Lease in-place value intangible	32,129
Land [Member] \| Venice, Florida [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial cost basis	16,850
Land and land estate	4,696
Building and improvements	11,753
Lease in-place value intangible	401
Office Building [Member] \| Auburn Hills, Michigan [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial cost basis	40,025
Land and land estate	4,416
Building and improvements	30,012
Lease in-place value intangible	5,597
Industrial property [Member] \| Houston, TX [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial cost basis	28,650
Land and land estate	4,674
Building and improvements	19,540
Lease in-place value intangible	4,436
Industrial property [Member] \| Brookshire, TX [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial cost basis	22,450
Land and land estate	2,388
Building and improvements	16,614
Lease in-place value intangible	3,448
Industrial property [Member] \| Canton, Mississippi [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial cost basis	89,300
Land and land estate	5,077
Building and improvements	71,289
Lease in-place value intangible	12,934
Industrial property [Member] \| Thomson, Georgia [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial cost basis	10,144
Land and land estate	909
Building and improvements	7,746
Lease in-place value intangible	1,489
Industrial property [Member] \| Oak Creek, Wisconsin [Member]
Investments in Real Estate and Real Estate Under Construction [Line Items]
Initial cost basis	22,139
Land and land estate	3,015
Building and improvements	15,300
Lease in-place value intangible	$ 3,824

Investments in Real Estate and Real Estate Under Construction [Line Items]

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 30

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

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- Definition

This element represents the amount of value allocated by a lessor (acquirer) to lease agreements which exist at acquisition of a leased property. Such amount may include the value assigned to existing tenant relationships and excludes the market adjustment component of the value assigned for above or below-market leases acquired.

+ References

No definition available.

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- Definition

Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements.

+ 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 210.7-03.1(d))

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- Definition

Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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