Land, Buildings and Improvements and Assets Held for Sale - Narratives (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 30, 2020 USD ($) property	Sep. 30, 2020 USD ($) property $ / €	Sep. 30, 2019 USD ($) property	Sep. 30, 2020 USD ($) property $ / €	Sep. 30, 2019 USD ($) property	Dec. 31, 2019 USD ($) property $ / €
Real Estate Properties
Increase in value of balance sheet item due to foreign currency translation		$ 34,170	$ (37,412)	$ (4,183)	$ (41,772)
Direct financing lease, net investments reclassified		(715,541)		(715,541)		$ (896,549)
Investments in real estate
Payment to acquire real estate				350,120	351,582
Capitalized construction cost				$ 198,100
Number of construction projects | property				4		3
Unfunded commitment		80,800		$ 80,800		$ 227,800
Interest income from direct financing leases		17,600	$ 25,400	56,500	$ 77,300
Assets held for sale, net		10,626		10,626		$ 104,010
Subsequent Events
Investments in real estate
Payment to acquire real estate	$ 186,800
Office Space in New York
Investments in real estate
Right of use asset		59,900		59,900
Lease liability		$ 61,400		$ 61,400
Properties disposed of by sale
Investments in real estate
Number of properties sold | property		4	4	8	9
Properties disposed of by sale | Subsequent Events
Real Estate Properties
Number of Properties | property	1
Asset held for sale, not in discontinued operations
Real Estate Properties
Number of Properties | property		2		2		1
Investments in real estate
Assets held for sale, net		$ 10,600		$ 10,600		$ 104,000
In-place lease
Investments in real estate
Payment to acquire real estate				$ 53,900
Finite lived intangible assets useful life				19 years 4 months 24 days
Assets held for sale, net		1,233		$ 1,233		0
Above-market rent
Investments in real estate
Payment to acquire real estate				$ 8,200
Finite lived intangible assets useful life				18 years 8 months 12 days
Net investments in direct financing lease
Investments in real estate
Number of properties sold | property				1
Land
Investments in real estate
Payment to acquire real estate				$ 39,100
Building
Investments in real estate
Payment to acquire real estate				253,400
Net Lease Intangible
Investments in real estate
Payment to acquire real estate				62,100
Construction in progress
Investments in real estate
Total capitalized costs				168,107
Land, buildings and improvements
Investments in real estate
Assets held for sale, net		12,210		$ 12,210		$ 105,573
Land, buildings and improvements | Properties disposed of by sale
Investments in real estate
Number of properties sold | property				7
Decrease in carrying value of real estate				$ 40,000
Operating Lease
Real Estate Properties
Increase in value of balance sheet item due to foreign currency translation				96,400
Depreciation		64,900	$ 58,300	192,900	$ 169,900
Investments in real estate
Payment to acquire real estate				354,612
Acquisition related costs				8,900
Land, Buildings and Improvements — Operating Properties
Real Estate Properties
Depreciation		$ 700	$ 800	$ 2,100	$ 6,200
Self-storage | Land, Buildings and Improvements — Operating Properties
Real Estate Properties
Number of Properties | property		10		10		10
Hotel | Land, Buildings and Improvements — Operating Properties
Real Estate Properties
Number of Properties | property		1		1		1
Reclassification
Real Estate Properties
Direct financing lease, net investments reclassified		$ 166,000		$ 166,000
Reclassification | Net investments in direct financing lease
Real Estate Properties
Number of Properties | property		55		55
EUR
Real Estate Properties
Increase in exchange rate				4.20%
Foreign currency exchange rate | $ / €		1.1708		1.1708		1.1234