2016 Acquisitions (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) property
Business Acquisition [Line Items]
Payments to acquire businesses				$ 1,428,944
Payments to acquire real estate		$ 265,907	$ 664,684	1,413,595
Net real estate property		$ 20,093,657	$ 20,622,454
Other 2016 Acquisitions
Business Acquisition [Line Items]
Payments to acquire real estate				$ 42,300
Other 2016 Acquisitions | Triple Net Leased Properties
Business Acquisition [Line Items]
Number of real estate properties acquired | property				1
Other 2016 Acquisitions | Medical Office Buildings
Business Acquisition [Line Items]
Number of real estate properties acquired | property				2
Research and Innovation Center
Business Acquisition [Line Items]
Payments to acquire businesses	$ 1,500,000