Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment revenue information
Total revenue	$ 328,886	$ 300,170	$ 647,181	$ 598,195
Rental revenue
Segment revenue information
Total revenue	313,870	288,049	620,418	573,870
Tenant reimbursements
Segment revenue information
Total revenue	11,395	11,756	22,695	22,985
Other revenue
Segment revenue information
Total revenue	3,621	365	4,068	1,340
Apparel | Rental revenue
Segment revenue information
Total revenue	4,210	4,928	8,541	9,895
Automotive service | Rental revenue
Segment revenue information
Total revenue	7,021	6,298	14,030	11,841
Automotive tire services | Rental revenue
Segment revenue information
Total revenue	7,708	7,616	15,147	14,775
Beverages | Rental revenue
Segment revenue information
Total revenue	7,836	7,758	15,673	15,516
Child care | Rental revenue
Segment revenue information
Total revenue	5,216	4,845	10,916	10,332
Convenience stores | Rental revenue
Segment revenue information
Total revenue	34,008	26,965	61,869	55,268
Dollar stores | Rental revenue
Segment revenue information
Total revenue	23,237	22,757	46,487	45,508
Drug stores | Rental revenue
Segment revenue information
Total revenue	32,436	31,614	64,775	63,245
Financial services | Rental revenue
Segment revenue information
Total revenue	6,890	7,159	13,891	14,318
General merchandise | Rental revenue
Segment revenue information
Total revenue	7,290	5,395	14,159	10,756
Grocery stores | Rental revenue
Segment revenue information
Total revenue	15,673	13,597	31,338	23,759
Health and fitness | Rental revenue
Segment revenue information
Total revenue	23,614	21,789	47,057	43,394
Home improvement | Rental revenue
Segment revenue information
Total revenue	9,339	7,090	18,583	14,010
Motor vehicle dealerships | Rental revenue
Segment revenue information
Total revenue	5,712	5,755	12,948	12,491
Restaurants-casual dining | Rental revenue
Segment revenue information
Total revenue	11,029	10,716	21,989	21,606
Restaurants-quick service | Rental revenue
Segment revenue information
Total revenue	17,083	14,517	33,362	28,853
Theaters | Rental revenue
Segment revenue information
Total revenue	17,565	13,114	35,335	26,458
Transportation services | Rental revenue
Segment revenue information
Total revenue	15,762	15,633	31,548	31,021
Wholesale club | Rental revenue
Segment revenue information
Total revenue	9,341	9,413	18,873	18,827
Other non-reportable segments | Rental revenue
Segment revenue information
Total revenue	$ 52,900	$ 51,090	$ 103,897	$ 101,997