Segments - Reconciliation of Net Operating Income to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Depreciation and amortization	$ (9,278)	$ (9,475)
General and administrative expenses	(2,961)	(2,986)
Acquisition, development and other pursuit costs	(84)	(47)
Impairment charges	0	(4)
Interest income	2,232	1,398
Interest expense	(4,373)	(4,535)
Gain on real estate dispositions	0	3,395
Change in fair value of interest rate derivatives	969	294
Other income	114	37
Income tax (provision) benefit	266	(302)
Net income	6,983	8,753
Operating Segments
Gross profit	20,098	20,978
Segment Reconciling Items
Depreciation and amortization	(9,278)	(9,475)
General and administrative expenses	(2,961)	(2,986)
Acquisition, development and other pursuit costs	(84)	(47)
Impairment charges	0	(4)
Interest income	2,232	1,398
Interest expense	(4,373)	(4,535)
Gain on real estate dispositions	0	3,395
Change in fair value of interest rate derivatives	969	294
Other income	114	37
Income tax (provision) benefit	$ 266	$ (302)