Segment Information - Revenue (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)	Dec. 31, 2016 segment
Segment revenue information
Rental revenue	$ 288,049	$ 260,056	$ 573,870	$ 516,857
Tenant reimbursements	11,756	11,112	22,985	20,217
Other revenue	365	(129)	1,340	1,081
Total revenue	300,170	271,039	598,195	538,155
Apparel
Segment revenue information
Rental revenue	4,928	4,879	9,895	9,754
Automotive service
Segment revenue information
Rental revenue	6,298	4,814	11,841	9,491
Automotive tire services
Segment revenue information
Rental revenue	7,616	7,220	14,775	14,484
Beverages
Segment revenue information
Rental revenue	7,758	6,404	15,516	12,809
Child care
Segment revenue information
Rental revenue	4,845	4,845	10,332	9,937
Convenience stores
Segment revenue information
Rental revenue	26,965	22,789	55,268	45,653
Dollar stores
Segment revenue information
Rental revenue	22,757	22,728	45,508	45,324
Drug stores
Segment revenue information
Rental revenue	31,614	28,638	63,245	57,059
Financial services
Segment revenue information
Rental revenue	7,159	4,252	14,318	8,565
General merchandise
Segment revenue information
Rental revenue	5,395	4,301	10,756	8,560
Grocery stores
Segment revenue information
Rental revenue	13,597	7,408	23,759	15,054
Health and fitness
Segment revenue information
Rental revenue	21,789	21,545	43,394	42,849
Home improvement
Segment revenue information
Rental revenue	7,090	6,099	14,010	12,153
Motor vehicle dealerships
Segment revenue information
Rental revenue	5,755	5,595	12,491	9,809
Restaurants-casual dining
Segment revenue information
Rental revenue	10,716	10,633	21,606	20,468
Restaurants-quick service
Segment revenue information
Rental revenue	14,517	12,482	28,853	25,276
Sporting goods
Segment revenue information
Rental revenue	4,729	5,316	9,174	9,872
Theaters
Segment revenue information
Rental revenue	13,114	12,708	26,458	26,157
Transportation services
Segment revenue information
Rental revenue	15,633	13,752	31,021	26,842
Wholesale club
Segment revenue information
Rental revenue	9,413	9,369	18,827	18,738
Other
Segment revenue information
Rental revenue	$ 46,361	$ 44,279	$ 92,823	$ 88,003
Number of Non Reportable Segments | segment	27		27		27