Operating Leases - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) state property	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) state property	Jun. 30, 2018 USD ($)
Operating Leases
Number of properties owned	5,951		5,951
Number of U.S. states where properties are owned (states) | state	49		49
Percentage rent received | $	$ 495	$ 449	$ 4,100	$ 3,800
Single-tenant properties
Operating Leases
Number of properties owned	5,922		5,922
Single-tenant properties as percentage of total properties	99.50%		99.50%
Properties available for lease or sale
Operating Leases
Number of properties owned	102		102