Real Estate Investments and Related Intangibles - Property Acquisitions (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($) property	Jun. 30, 2018 USD ($) property
Acquisition, 2019 [Member]
Business Acquisition [Line Items]
Number of properties acquired | property	33
Total purchase price of assets acquired	$ 200,459
Capitalized acquisition costs	1,000
Acquisitions 2018 [Member]
Business Acquisition [Line Items]
Number of properties acquired | property		19
Total purchase price of assets acquired		$ 181,240
Capitalized acquisition costs		$ 1,100
Build-to-suit Development Project [Member] | Acquisition, 2019 [Member]
Business Acquisition [Line Items]
Capitalized acquisition costs	500
Development in process	$ 16,400
Number of real estate properties acquired | property	1
Remaining investment	$ 11,900
Development in progress expected period of completion	12 months