CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Cash Flows from Operating Activities
Net income	$ 15,756	$ 12,283	$ 45,460	$ 42,119
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation			17,808	14,366
Amortization			13,935	8,590
Amortization from financing and credit facility costs			768	730
Stock-based compensation			2,171	1,748
Provision for impairment	488	0	1,651	0
(Gain) loss on sale of assets			(10,949)	(10,045)
(Increase) decrease in accounts receivable			(5,122)	(4,192)
(Increase) decrease in other assets			(934)	(148)
Increase (decrease) in accounts payable and accrued expenses			923	1,837
Increase (decrease) in deferred revenue			(758)	(371)
Increase (decrease) in accrued interest			(706)	549
Increase (decrease) in tenant deposits			5	2
Net Cash Provided by Operating Activities			64,252	55,185
Cash Flows from Investing Activities
Acquisition of real estate investments and other assets			(352,085)	(241,132)
Development of real estate investments and other assets (including capitalized interest of $381 in 2018 and $297 in 2017)			(17,390)	(27,240)
Payment of leasing costs			(1,191)	(544)
Net proceeds from sale of assets			60,038	29,414
Net Cash Used In Investing Activities			(310,628)	(239,502)
Cash Flows from Financing Activities
Proceeds from common stock offerings, net			159,604	136,733
Repurchase of common shares			(1,142)	(1,108)
Unsecured revolving credit facility borrowings			260,000	184,000
Unsecured revolving credit facility repayments			(260,000)	(198,000)
Payments of mortgage notes payable			(26,915)	(1,794)
Payments of unsecured term loans			(571)	(549)
Senior unsecured notes proceeds			125,000	100,000
Dividends paid			(49,018)	(40,392)
Distributions to Non-Controlling Interest			(549)	(520)
Payments for financing costs			(568)	(159)
Net Cash Provided by Financing Activities			205,841	178,211
Net Increase (Decrease) in Cash and Cash Equivalents			(40,535)	(6,106)
Cash and cash equivalents and restricted deposits, beginning of period			58,782	33,395	$ 33,395
Cash and cash equivalents and restricted deposits, end of period	$ 18,247	$ 27,289	18,247	27,289	$ 58,782
Supplemental Disclosure of Cash Flow Information
Cash paid for interest (net of amounts capitalized)			18,944	12,658
Cash paid (refunded) for income tax			387	0
Supplemental Disclosure of Non-Cash Investing and Financing Activities
Shares issued under equity incentive plans (in dollars)			2,381	3,022
Dividends and limited partners' distributions declared and unpaid			$ 18,808	$ 14,930