Segments - Reconciliation of Net Operating Income to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Amortization of finance leases	$ (147)			$ (145)			$ (440)	$ (230)
General and administrative expenses	(2,601)			(2,977)			(9,382)	(9,329)
Acquisition, development and other pursuit costs	(26)			(93)			(555)	(550)
Impairment charges	(47)			0			(205)	0
Gain on real estate dispositions	3,612			4,699			6,388	4,699
Interest income	4,417			5,710			16,055	16,622
Interest expense on indebtedness	(7,294)			(8,828)			(22,252)	(22,205)
Interest expense on finance leases	(229)			(228)			(686)	(340)
Equity in income of unconsolidated real estate entities	0			0			0	273
Change in fair value of derivatives and other	318			(530)			(1,424)	(3,926)
Unrealized credit loss release (provision)	33			0			(227)	0
Other income (expense), net	177			362			521	426
Income tax benefit	28			199			220	339
Net income	10,826	$ 12,309	$ 9,135	12,063	$ 5,826	$ 6,514	32,270	24,403
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gross profit	26,761			29,359			86,489	77,498
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Depreciation and amortization	(14,176)			(15,465)			(42,232)	(38,874)
Amortization of finance leases	(147)			(145)			(440)	(230)
General and administrative expenses	(2,601)			(2,977)			(9,382)	(9,329)
Acquisition, development and other pursuit costs	(26)			(93)			(555)	(550)
Impairment charges	(47)			0			(205)	0
Gain on real estate dispositions	3,612			4,699			6,388	4,699
Interest income	4,417			5,710			16,055	16,622
Interest expense on indebtedness	(7,294)			(8,828)			(22,252)	(22,205)
Interest expense on finance leases	(229)			(228)			(686)	(340)
Equity in income of unconsolidated real estate entities	0			0			0	273
Change in fair value of derivatives and other	318			(530)			(1,424)	(3,926)
Unrealized credit loss release (provision)	33			0			(227)	0
Other income (expense), net	177			362			521	426
Income tax benefit	$ 28			$ 199			$ 220	$ 339