Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment revenue information
Total revenue	$ 338,081	$ 306,920	$ 985,262	$ 905,115
Rental revenue
Segment revenue information
Total revenue	324,773	293,455	945,191	867,325
Tenant reimbursements
Segment revenue information
Total revenue	12,479	11,933	35,174	34,918
Other revenue
Segment revenue information
Total revenue	829	1,532	4,897	2,872
Apparel | Rental revenue
Segment revenue information
Total revenue	4,042	4,718	12,582	14,613
Automotive service | Rental revenue
Segment revenue information
Total revenue	7,120	6,416	21,150	18,257
Automotive tire services | Rental revenue
Segment revenue information
Total revenue	7,460	7,383	22,607	22,158
Beverages | Rental revenue
Segment revenue information
Total revenue	7,908	7,829	23,581	23,345
Child care | Rental revenue
Segment revenue information
Total revenue	5,255	5,062	16,172	15,395
Convenience stores | Rental revenue
Segment revenue information
Total revenue	39,384	27,874	101,254	83,143
Dollar stores | Rental revenue
Segment revenue information
Total revenue	23,903	22,738	70,390	68,246
Drug stores | Rental revenue
Segment revenue information
Total revenue	32,431	31,635	97,206	94,880
Financial services | Rental revenue
Segment revenue information
Total revenue	7,850	7,058	21,741	21,377
General merchandise | Rental revenue
Segment revenue information
Total revenue	7,453	6,296	21,613	17,263
Grocery stores | Rental revenue
Segment revenue information
Total revenue	16,095	13,450	47,433	37,209
Health and fitness | Rental revenue
Segment revenue information
Total revenue	23,754	22,416	70,812	65,810
Home improvement | Rental revenue
Segment revenue information
Total revenue	9,678	7,816	28,261	21,826
Motor vehicle dealerships | Rental revenue
Segment revenue information
Total revenue	5,711	5,749	18,660	18,240
Restaurants-casual dining | Rental revenue
Segment revenue information
Total revenue	12,355	11,073	34,344	32,853
Restaurants-quick service | Rental revenue
Segment revenue information
Total revenue	18,673	14,659	52,035	43,337
Theaters | Rental revenue
Segment revenue information
Total revenue	17,479	14,947	52,814	41,405
Transportation services | Rental revenue
Segment revenue information
Total revenue	16,105	15,635	47,653	46,656
Wholesale club | Rental revenue
Segment revenue information
Total revenue	9,345	9,414	28,218	28,241
Other non-reportable segments | Rental revenue
Segment revenue information
Total revenue	$ 52,772	$ 51,287	$ 156,665	$ 153,071