Real Estate Assets (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) propertyUnit shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)
Dispositions [Abstract]
Gain/(loss) on disposition of property	$ 318		$ 6,703	$ 153,385	$ 6,703
Impairments [Abstract]
Impairments of real estate assets	1,778		$ 531	$ 1,778	$ 531
Raleigh NC Land Acquisition [Member]
Acquisitions [Abstract]
Acquisition purchase price	2,300
Nashville TN Land Acquisition [Member]
Acquisitions [Abstract]
Acquisition purchase price		$ 6,200
Issuance of Common Units in acquisition (in units) | shares		118,592
2020 Dispositions [Member]
Dispositions [Abstract]
Number of buildings sold | propertyUnit		41
Purchase price of real estate	2,800	$ 338,400
Closing credits excluded for unfunded building and/or tenant improvements		3,800
Gain/(loss) on disposition of property	(100)	$ 153,100
2016 Land Disposition [Member]
Dispositions [Abstract]
Gain/(loss) on disposition of property	400
2020 Impairments [Member]
Impairments [Abstract]
Impairments of real estate assets	$ 1,800