CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
OPERATING ACTIVITIES:
Net income	$ 73,399,000	$ 57,815,000	$ 51,327,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization (continuing and discontinued operations)	25,529,000	24,706,000	22,153,000
Stock-based compensation expense	3,253,000	2,591,000	1,819,000
Gain on sale of real estate, net	(4,959,000)	(1,605,000)	(16,000)
Straight-line rental income—continuing and discontinued operations	(3,002,000)	(3,955,000)	(3,264,000)
Provision (recovery) for doubtful accounts	32,000	2,180,000	(101,000)
Non-cash interest related to earn-out liabilities	18,000	256,000	439,000
Other non-cash items, net	1,653,000	1,441,000	1,460,000
Decrease in interest receivable	72,000	32,000	535,000
Increase in accrued interest payable	132,000	145,000	1,923,000
Net change in other assets and liabilities	(365,000)	3,519,000	545,000
Net cash provided by operating activities	95,762,000	87,125,000	76,820,000
INVESTING ACTIVITIES:
Investment in real estate properties, net	(11,650,000)	(19,040,000)	(166,750,000)
Investment in real estate developments, net	(34,135,000)	(23,605,000)	(9,957,000)
Investment in real estate capital improvements, net	(13,967,000)	(6,992,000)	(1,132,000)
Capitalized interest	(1,506,000)	(932,000)	(130,000)
Proceeds from sale of real estate investments, net	33,593,000	11,001,000	1,271,000
Investment in real estate mortgages	(9,374,000)	(129,358,000)	(7,719,000)
Principal payments received on mortgage loans receivable	9,155,000	1,933,000	21,633,000
Proceeds from redemption of marketable securities			6,500,000
Advances under notes receivable	(1,263,000)	(1,004,000)	(2,930,000)
Principal payments received on notes receivable	113,000	3,110,000	569,000
Net cash used in investing activities	(29,034,000)	(164,887,000)	(158,645,000)
FINANCING ACTIVITIES:
Bank borrowings	37,500,000	93,000,000	153,500,000
Repayment of bank borrowings	(58,500,000)	(187,500,000)	(94,000,000)
Proceeds from issuance of senior unsecured notes	30,000,000	70,000,000	85,800,000
Principal payments on senior unsecured notes	(4,167,000)
Principal payments on mortgage loan payable and bonds payable	(2,035,000)	(600,000)	(565,000)
Payment of earn-out liabilities		(7,000,000)
Proceeds from common stock offerings	24,644,000	176,260,000
Stock option exercises	1,071,000	523,000	1,926,000
Distributions paid to stockholders	(74,431,000)	(66,904,000)	(57,785,000)
Redemption of non-controlling interests			(2,764,000)
Distributions paid to non-controlling interests		(7,000)	(78,000)
Financing costs paid	(2,132,000)	(171,000)	(1,426,000)
Other	(219,000)	(252,000)
Net cash (used in) provided by financing activities	(48,269,000)	77,349,000	84,608,000
Increase (decrease) in cash and cash equivalents	18,459,000	(413,000)	2,783,000
Cash and cash equivalents, beginning of period	6,778,000	7,191,000	4,408,000
Cash and cash equivalents, end of period	25,237,000	6,778,000	7,191,000
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid	$ 13,694,000	$ 11,398,000	$ 7,452,000