Investments - Summary of Owned Real Estate Activity (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) Property	Mar. 31, 2019 USD ($)
Dollar Amount of Investments
Impairments	$ (40,164)	$ (3,692)
Ending balance	6,300,000
Net balance	$ 5,414,257
Held in Use
Number of Properties
Beginning balance (in properties) | Property	1,750
Acquisitions/improvements (in properties) | Property	27
Dispositions of real estate (in properties) | Property	(5)
Transfers to Held for Sale (in properties) | Property	(5)
Transfers from Held for Sale (in properties) | Property	0
Impairments (in properties) | Property	0
Write-off of intangibles (in properties) | Property	0
Other (in properties) | Property	0
Ending balance (in properties) | Property	1,767
Dollar Amount of Investments
Beginning balance	$ 6,140,775
Acquisitions	215,011
Dispositions	(17,114)
Transfers to Held for Sale	(3,362)
Transfers from Held for Sale	0
Impairments	(40,468)
Write-off of intangibles	(26,594)
Other	(1,330)
Ending balance	6,266,918
Accumulated depreciation and amortization	(855,787)
Net balance	$ 5,411,131
Held for Sale
Number of Properties
Beginning balance (in properties) | Property	2
Acquisitions/improvements (in properties) | Property	0
Dispositions of real estate (in properties) | Property	(2)
Transfers to Held for Sale (in properties) | Property	5
Transfers from Held for Sale (in properties) | Property	0
Impairments (in properties) | Property	0
Write-off of intangibles (in properties) | Property	0
Other (in properties) | Property	0
Ending balance (in properties) | Property	5
Dollar Amount of Investments
Beginning balance	$ 1,223
Acquisitions	0
Dispositions	(1,223)
Transfers to Held for Sale	3,362
Transfers from Held for Sale	0
Impairments	0
Write-off of intangibles	0
Other	0
Ending balance	3,362
Accumulated depreciation and amortization	(236)
Net balance	$ 3,126
Total
Number of Properties
Beginning balance (in properties) | Property	1,752
Acquisitions/improvements (in properties) | Property	27
Dispositions of real estate (in properties) | Property	(7)
Transfers to Held for Sale (in properties) | Property	0
Transfers from Held for Sale (in properties) | Property	0
Impairments (in properties) | Property	0
Write-off of intangibles (in properties) | Property	0
Other (in properties) | Property	0
Ending balance (in properties) | Property	1,772
Dollar Amount of Investments
Beginning balance	$ 6,141,998
Acquisitions	215,011
Dispositions	(18,337)
Transfers to Held for Sale	0
Transfers from Held for Sale	0
Impairments	(40,468)
Write-off of intangibles	(26,594)
Other	(1,330)
Ending balance	6,270,280
Accumulated depreciation and amortization	(856,023)
Net balance	$ 5,414,257