Real Estate Investments (Details) $ in Thousands, ft² in Millions	3 Months Ended
Mar. 31, 2019 USD ($) ft² site	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($) ft²
Real Estate Properties [Line Items]
Number of Real Estate Properties	694		645
Land Subject to Ground Leases \| ft²	11.9		11.2
Net Real Estate Investments	$ 1,780,769		$ 1,661,334
Number of Development and Partner Capital Solutions Projects Construction \| site	9
Number of properties sold	2
Proceeds from Sale of Real Estate	$ 9,800
Gains (Losses) on Sales of Investment Real Estate	3,400
Provision for impairment	(416)	$ 0
Impairment of Long-Lived Assets Held-for-use	400
Business Acquisition 2019 [Member]
Real Estate Properties [Line Items]
Payments to Acquire Property, Plant, and Equipment	$ 141,700
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (in year)	12 years 9 months 18 days
Retail Net Lease Assets Purchased	48
Number Of States Properties Located	22
Number of Contracts or Customers Comprising Ten Percent or More Of Company's Total Assets or Total Rent	0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Land	$ 34,900
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Buildings	92,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	14,400
Contingent consideration	$ 0

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Amount of real estate acquired, at the acquisition date.

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Area of land subject to a ground lease.

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