Operating Leases - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) state property	Mar. 31, 2018 USD ($)
Operating Leases
Number of properties owned	5,876
Number of U.S. states where properties are owned (states) | state	49
Percentage rent received | $	$ 3.6	$ 3.3
Single-tenant properties
Operating Leases
Number of properties owned	5,847
Single-tenant properties as percentage of total properties	99.50%
Properties available for lease or sale
Operating Leases
Number of properties owned	102