Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment revenue information
Rental (including reimbursable)	$ 412,157	$ 354,037
Other	2,184	328
Total revenue	414,341	354,365
Automotive service
Segment revenue information
Rental (including reimbursable)	8,670	7,213
Automotive tire services
Segment revenue information
Rental (including reimbursable)	7,833	7,777
Beverages
Segment revenue information
Rental (including reimbursable)	7,996	7,915
Child care
Segment revenue information
Rental (including reimbursable)	9,481	7,827
Convenience stores
Segment revenue information
Rental (including reimbursable)	46,733	41,214
Dollar stores
Segment revenue information
Rental (including reimbursable)	31,391	24,986
Drug stores
Segment revenue information
Rental (including reimbursable)	35,299	33,170
Financial services
Segment revenue information
Rental (including reimbursable)	7,543	7,718
General merchandise
Segment revenue information
Rental (including reimbursable)	11,316	6,911
Grocery stores - U.S.
Segment revenue information
Rental (including reimbursable)	19,509	16,124
Grocery stores - U.K.
Segment revenue information
Rental (including reimbursable)	10,405	0
Health and fitness
Segment revenue information
Rental (including reimbursable)	28,278	26,225
Home improvement
Segment revenue information
Rental (including reimbursable)	11,309	9,815
Restaurants-casual dining
Segment revenue information
Rental (including reimbursable)	12,538	11,290
Restaurants-quick service
Segment revenue information
Rental (including reimbursable)	23,308	21,730
Theaters - U.S.
Segment revenue information
Rental (including reimbursable)	24,567	17,656
Transportation services
Segment revenue information
Rental (including reimbursable)	16,187	16,026
Wholesale club
Segment revenue information
Rental (including reimbursable)	9,588	9,593
Other non-reportable segments and tenant reimbursements
Segment revenue information
Rental (including reimbursable)	$ 90,206	$ 80,847