Real Estate Investments (Details Textual) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($) ft²	Sep. 30, 2018 USD ($) ft²	Dec. 31, 2017 USD ($) ft²
Real Estate Properties [Line Items]
Property Subject to or Available for Operating Lease, Gross	$ 59,600	$ 59,600
Number of Real Estate Properties	520	520	436
Land Subject to Ground Leases \| ft²	10.0	10.0	8.7
Real Estate Investment Property, Net	$ 1,424,828	$ 1,424,828	$ 1,214,016
Impairment of Long-Lived Assets Held-for-use	500	1,700
Gains (Losses) on Sales of Investment Real Estate	3,900	9,900
Options Exercised [Member]
Real Estate Properties [Line Items]
Proceeds from Sale of Real Estate		3,900
Gains (Losses) on Sales of Investment Real Estate		1,000
Five Development And PCS Projects [Member]
Real Estate Properties [Line Items]
Property Subject to or Available for Operating Lease, Gross	14,000	14,000
Five Real Estate Properties [Member]
Real Estate Properties [Line Items]
Proceeds from Sale of Real Estate	$ 29,600	$ 56,400
Seventy Nine Retail Net Lease Assets [Member]
Real Estate Properties [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (in year)	11 years 6 months	12 years 3 months 18 days
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Land	$ 81,600	$ 81,600
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Buildings	174,400	174,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	93,900	93,900
Seventy Nine Retail Net Lease Assets [Member] \| Five Development And PCS Projects [Member]
Real Estate Properties [Line Items]
Payments to Acquire Property, Plant, and Equipment	$ 150,000	$ 349,900

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of facility held for productive use including, but not limited to, office, production, storage and distribution facilities, acquired at the acquisition date.

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