CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended					9 Months Ended		12 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
OPERATING ACTIVITIES:
Net income	$ 34,937,000	$ 20,359,000	$ 19,834,000	$ 20,616,000	$ 21,513,000	$ 124,232,000	$ 67,506,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization						28,159,000	28,186,000
Stock-based compensation expense						4,384,000	3,967,000
Impairment charges							1,880,000
Gain on sale of real estate, net	(14,353,000)					(62,698,000)	(5,054,000)
Income from unconsolidated joint ventures	(746,000)			(615,000)		(2,103,000)	(1,635,000)
Income distributions from unconsolidated joint ventures						1,727,000	1,236,000
Insurance proceeds for damaged property						2,619,000
Payment for remediation of damaged property						(455,000)
Straight-line rental income						(8,629,000)	(7,362,000)
Lease incentives funded						(1,272,000)	(5,713,000)
Amortization of lease incentives						1,651,000	1,681,000
Provision for doubtful accounts	106,000			(96,000)		76,000	(139,000)
Non-cash interest related to contingent liabilities						377,000	476,000
Non-cash income related to earn-out and related lease inducement write-off							(842,000)
Other non-cash items, net						923,000	958,000
Increase in interest receivable						(4,240,000)	(3,967,000)
Decrease in accrued interest payable						(1,808,000)	(567,000)
Net change in other assets and liabilities						495,000	(4,477,000)
Net cash provided by operating activities						83,438,000	76,134,000
INVESTING ACTIVITIES:
Investment in real estate properties						(40,408,000)	(54,804,000)
Investment in real estate developments						(25,717,000)	(13,939,000)
Investment in real estate capital improvements						(2,063,000)	(2,308,000)
Capitalized interest						(850,000)	(627,000)
Proceeds from sale of real estate, net						82,340,000	14,106,000
Investment in real estate mortgage loans receivable						(20,530,000)	(9,333,000)
Principal payments received on mortgage loans receivable						1,636,000	17,351,000
Investments in unconsolidated joint ventures						(580,000)	(3,847,000)
Payment of working capital reserve							(439,000)
Advances and originations under notes receivable						(50,000)
Principal payments received on notes receivable						3,848,000	25,000
Net cash used in investing activities						(2,374,000)	(53,815,000)
FINANCING ACTIVITIES:
Bank borrowings						96,500,000	64,500,000
Repayment of bank borrowings						(73,000,000)	(116,600,000)
Proceeds from issuance of senior unsecured notes							100,000,000
Principal payments on senior unsecured notes						(20,166,000)	(19,167,000)
Proceeds from common stock issued						1,005,000	14,578,000
Stock option exercises						123,000	202,000
Distributions paid to stockholders						(67,768,000)	(67,664,000)
Contribution from non-controlling interests						3,963,000
Financing costs paid						(3,162,000)	(363,000)
Other						(1,201,000)	(1,954,000)
Net cash used in financing activities						(63,706,000)	(26,468,000)
Increase (decrease) in cash, cash equivalents and restricted cash						17,358,000	(4,149,000)
Cash, cash equivalents and restricted cash, beginning of period		$ 5,213,000	3,842,000		$ 7,991,000	5,213,000	7,991,000	$ 7,991,000
Cash, cash equivalents and restricted cash, end of period	$ 22,571,000		$ 5,213,000	$ 3,842,000		22,571,000	3,842,000	$ 5,213,000
Supplemental disclosure of cash flow information:
Interest paid						$ 23,869,000	$ 21,877,000