Segments - Reconciliation of Net Operating Income to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net operating income	$ 8,267	$ 6,710	$ 16,733	$ 12,709
Depreciation and amortization	(9,304)	(8,602)	(18,779)	(16,751)
General and administrative expenses	(2,678)	(2,224)	(5,664)	(4,708)
Acquisition, development and other pursuit costs	(369)	(437)	(416)	(1,141)
Impairment charges	(27)	0	(31)	(35)
Interest income	1,658	722	3,056	904
Interest expense	(4,494)	(3,978)	(9,029)	(7,769)
Gain on real estate dispositions	0	13	3,395	26,687
Change in fair value of interest rate derivatives	(81)	(373)	213	(2,762)
Other income	43	43	80	119
Income tax provision	(450)	(6)	(752)	(224)
Net income	4,943	3,131	13,696	29,664
Operating Segments
Net operating income	20,645	17,973	41,623	35,344
Segment Reconciling Items
Depreciation and amortization	(9,304)	(8,602)	(18,779)	(16,751)
General and administrative expenses	(2,678)	(2,224)	(5,664)	(4,708)
Acquisition, development and other pursuit costs	(369)	(437)	(416)	(1,141)
Impairment charges	(27)	0	(31)	(35)
Interest income	1,658	722	3,056	904
Interest expense	(4,494)	(3,978)	(9,029)	(7,769)
Gain on real estate dispositions	0	13	3,395	26,687
Change in fair value of interest rate derivatives	(81)	(373)	213	(2,762)
Other income	43	43	80	119
Income tax provision	$ (450)	$ (6)	$ (752)	$ (224)