Segment Information - Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment revenue information
Total revenue	$ 318,295	$ 298,025
Rental revenue
Segment revenue information
Total revenue	306,548	285,821
Tenant reimbursements
Segment revenue information
Total revenue	11,300	11,229
Other revenue
Segment revenue information
Total revenue	447	975
Apparel | Rental revenue
Segment revenue information
Total revenue	4,331	4,966
Automotive service | Rental revenue
Segment revenue information
Total revenue	7,009	5,543
Automotive tire services | Rental revenue
Segment revenue information
Total revenue	7,439	7,159
Beverages | Rental revenue
Segment revenue information
Total revenue	7,836	7,758
Child care | Rental revenue
Segment revenue information
Total revenue	5,672	5,487
Convenience stores | Rental revenue
Segment revenue information
Total revenue	28,000	28,303
Dollar stores | Rental revenue
Segment revenue information
Total revenue	23,250	22,752
Drug stores | Rental revenue
Segment revenue information
Total revenue	32,242	31,631
Financial services | Rental revenue
Segment revenue information
Total revenue	7,020	7,159
General merchandise | Rental revenue
Segment revenue information
Total revenue	6,870	5,361
Grocery stores | Rental revenue
Segment revenue information
Total revenue	15,665	10,162
Health and fitness | Rental revenue
Segment revenue information
Total revenue	23,444	21,605
Home improvement | Rental revenue
Segment revenue information
Total revenue	9,244	6,919
Motor vehicle dealerships | Rental revenue
Segment revenue information
Total revenue	7,311	6,736
Restaurants-casual dining | Rental revenue
Segment revenue information
Total revenue	10,948	10,890
Restaurants-quick service | Rental revenue
Segment revenue information
Total revenue	16,249	14,336
Theaters | Rental revenue
Segment revenue information
Total revenue	17,770	13,344
Transportation services | Rental revenue
Segment revenue information
Total revenue	15,786	15,388
Wholesale club | Rental revenue
Segment revenue information
Total revenue	9,532	9,413
Other non-reportable segments | Rental revenue
Segment revenue information
Total revenue	$ 50,930	$ 50,909