Business and Organization - Narratives (Details) ft² in Millions	3 Months Ended
	Mar. 31, 2018 ft² segment property tenant	Dec. 31, 2017 property
Additional disclosures
Number of business segments | segment	2
Hotel
Additional disclosures
Number of real estate properties	1	2
Owned Real Estate
Additional disclosures
Number of real estate properties	886
Square footage of real estate properties | ft²	85.4
Number of tenants | tenant	208
Occupancy rate	99.70%
Owned Real Estate | Hotel
Additional disclosures
Number of real estate properties	2
Investment Management | CPA REITs
Additional disclosures
Number of real estate properties	462
Square footage of real estate properties | ft²	54.0
Number of tenants | tenant	206
Occupancy rate	99.40%
Investment Management | Managed Programs
Additional disclosures
Number of real estate properties	164
Square footage of real estate properties | ft²	19.9