Investments - Summary of Gross Investment Activity (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($) investmentLocation	Jun. 30, 2020 USD ($) investmentLocation	Dec. 31, 2020 USD ($)
Number of Investment Locations
Beginning balance | investmentLocation	1,181	1,000
Acquisitions of and additions to real estate investments | investmentLocation	125	73
Sales of investments in real estate | investmentLocation	(25)	(13)
Relinquishment of properties at end of ground lease term | investmentLocation		(3)
Investments in loans receivable | investmentLocation	45	3
Principal collections on and settlements of loans and direct financing lease receivables | investmentLocation	(1)
Ending balance | investmentLocation	1,325	1,060
Dollar Amount of Investments
Beginning balance	$ 2,528,673	$ 2,002,314
Acquisitions of and additions to real estate investments	341,878	207,774
Sales of investments in real estate	(42,859)	(21,882)
Relinquishment of properties at end of ground lease term		(1,931)
Provisions for impairment of real estate	(6,120)	(1,859)
Investments in loans receivable	85,365	9,656
Principal collections on and settlements of loans and direct financing lease receivables	(1,026)	(130)
Other	196	(1,328)
Ending balance	2,906,107	2,192,614
Less: accumulated depreciation and amortization	(165,731)	(113,235)	$ (136,097)
Net investments	$ 2,740,376	$ 2,079,379	$ 2,392,576