Investments - Additional Information (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020 USD ($) Property Investment Loan	Jun. 30, 2020 USD ($) Property Investment Loan	Jun. 30, 2019 USD ($) Investment Property	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($) Property Loan Investment	Dec. 31, 2018 USD ($)
Investments [Abstract]
Number of property locations of investments | Property	1,060	1,060			1,000
Number of property development in progress | Property	6	6			8
Number of real estate properties undeveloped land parcels | Property	1	1			1
Number of owned properties | Property	960	960			897
Number of properties owned as direct financing receivables | Property	11	11			8
Number of ground lease interests | Property	8	8			12
Number of real estate subject to direct financing leases | Property	1	1			1
Number of additional properties secured for mortgage loan receivable | Property	92	92			91
Number of mortgage loans receivable | Loan	9	9			6
Gross acquisition cost of real estate investments	$ 2,192,614	$ 2,192,614	$ 1,660,235		$ 2,002,314	$ 1,394,549
Real estate investments, at cost	2,089,815	2,089,815			1,908,919
Aggregate carrying amount of loans and direct financing lease receivable	$ 101,000	$ 101,000			$ 92,200
Number of investments | Investment	255	255			355
Investments	$ 364,800	$ 364,800			$ 601,300
Number of acquisitions individually represented more than five percentage of total investment activity | Investment		0	0
Number of loan receivable agreements secured | Loan	10	10			7
Aggregate carrying value of loans	$ 99,200	$ 99,200			$ 89,600
Partial repayment of loans	100	$ 100
Number of loan arrangements entered into | Property		3	3
Aggregate carrying value of loans entered into		$ 8,600
Credit risk, maximum exposure		99,200
Aggregate carrying amount of direct financing lease receivable	2,500	2,500			2,600
Allowance for loan losses	$ 704	$ 704		$ 200	$ 0